Wheel bearing and sealing device therefor

ABSTRACT

A wheel bearing includes a sealing device  5  positioned between inner and outer members  1  and  2 . This sealing device  5  includes an elastic member  14 , which eventually forms an encoder grid and is provided on a first annular sealing plate  11 . A second annular sealing plate  12  is provided with sealing lips  16   a  to  16   c . An engagement  18  between a cylindrical wall  11   a  of the first annular sealing plate  11  and the inner member  1  is provided with an elastic member  20  made of a material dissimilar to that for the elastic material  14 . This elastic member  20  may be a rubber coated layer, resin paint layer, a thin film of adhesive material or a ring-shaped rubber member. Thereby, any possible ingress of water across an engagement surface of the annular sealing plate is prevented, accompanied by increase of the lifetime of the bearing, with no problem associated with separation and displacement of the annular sealing plates. The magnetic flux density can also be easily secured.

BACKGROUND OF THE INVENTION

[0001] 1. (Field of the Invention)

[0002] The present invention generally relates to a sealing device in awheel bearing for an automobile or the like and, more particularly, tothe sealing device of a kind integrated together with an encoder grid.

[0003] 2. (Description of the Prior Art)

[0004] The wheel bearing including, as shown in FIG. 37, a sealingdevice 105 interposed between an inner member 101 and an outer member102 rotatable to each other through a circular row of rolling elements103 has been well known in the art. The sealing device 105 shown thereinincludes an encoder grid 106 integrated together therewith. In thisconnection, see the Japanese Laid-open Patent Publication No. 6-281018.The prior art sealing device 105 includes generally L-sectioned firstand second annular sealing plates 107 and 108 fitted respectively to theinner and outer members 101 and 102 with an elastically deformablesealing lip member 109 secured to the second annular sealing plate 108so as to intervene between the first and second annular sealing plates107 and 108. The first annular sealing plate 107 is generally referredto as a slinger. The encoder grid 106 is made of an elastic materialmixed with a powder of magnetic particles and is bonded by vulcanizationto the first annular sealing plate 107. This encoder grid 106 is of anannular configuration having a plurality of pairs of magneticallyopposite poles alternating over the circumference thereof and iscooperable with a magnetic sensor 110 disposed externally inface-to-face relation with the encoder grid 106 for detection of theencoder grid 106.

[0005] The first annular sealing plate 107 serving as the slinger andthe inner member 101 serving as a rotatable member are engaged with eachother under interference fit at an engagement interface 111. However, ithas been found that small quantity of water often ingresses externallyinto the wheel bearing through the engagement interface 111. Once wateringresses, the first and second annular sealing plates 107 and 108gather rust, resulting a premature wear of the sealing lip member 109.Also, the grease is prematurely degraded to such an extent as to resultin reduction of the lifetime of the wheel bearing.

[0006] In view of the foregoing, it has been suggested to reconfigurethe encoder grid 106 so that a portion of the elastic material formingthe encoder grid 106 extends to an inner peripheral surface of the firstannular sealing plate 107 to thereby increase the sealability at theengagement interface 111. However, since the elastic material formingthe encoder grid 106 is mixed with the powder of magnetic particles, notonly becomes the encoder grid 106 expensive to manufacture, but arequired sealing performance is difficult to attain. Also, formation ofa relatively thick rubber layer at the engagement interface 111 betweenthe first annular sealing plate 107 and the inner member 101 results inan insufficient engagement therebetween with the consequence that thereis a high risk of the first annular sealing plate 107 being separatedfrom the wheel bearing and/or displaced internally of the wheel bearing.

[0007] Although instead of the intervention of the elastic material thefirst annular sealing plate 107 may be made of a soft material tothereby increase the adherence, such soft material is normally of anon-magnetic nature and, therefore, the first annular sealing plate 107made of such material will fail to provide a magnetic core for theencoder grid 106, resulting in an insufficient density of magneticfluxes.

[0008] The first annular sealing plate 107 may exhibit a sufficientresistance to rusting if it is made of magnetic stainless steel (forexample, SUS 430MA) of a kind having a resistance to rusting comparableto that of SUS 304, rather than a generally utilized magnetic materialsuch as SUS 430 of a kind lacking a sufficient resistance to rusting.The magnetic stainless steel referred to above may be SUS 430MAconsisting of a stainless steel such as SUS 430 mixed with niobium, Nior the like to increase the resistance to rusting. As regards themagnetic flux density, SUS 430MA is comparable to SUS 430. However, notonly is the magnetic stainless steel referred to above expensive, buteven though such material is employed for the first annular sealingplate 107, ingress of water cannot be sufficiently prevented, andtherefore, reduction of the lifetime of the wheel bearing as a result ofdegradation of the grease in contact with water cannot be avoidedsufficiently.

[0009]FIG. 38 illustrates another prior art wheel bearing. In thisfigure, components identical with or similar to those shown in FIG. 37are shown by like reference numerals used in FIG. 37. The sealing device105 shown in FIG. 38 is shown as employed in the rolling bearing of atype having an inner race rotatable relative to an outer race. Thesealing device 105 includes a slinger 107 press-fitted to an outerperipheral end face of the inner race 101, a core metal 108 press-fittedto an inner peripheral end face of the outer race 102 in face-to-facerelation with the slinger 107, a sealing member 109 fitted to the coremetal 108 and held in sliding contact with the slinger 107, and a rubbermagnet 106 bonded by vulcanization to the slinger 107. The rubber magnet106 referred to above is a pulse generating ring generally used forspeed control of a vehicle such as, for example, an automobile. Theslinger 107 is of a structure including an cylindrical body 107 a havingan outer edge formed integrally with a radial flange 107 b thatprotrudes radially outwardly towards the outer race 102. The core metal108 is of a structure including a cylindrical body 108 a press-fitted tothe inner peripheral end face of the outer race 102 and formedintegrally with an radial flange 108 b that protrudes radially inwardlytowards the inner race 101 from an inner end thereof adjacent thecircular row of the rolling elements 103. An outer end 108 aa of thehollow cylindrical body 108 a is slightly radially inwardly bent toaccommodate the sealing member 109.

[0010] The sealing device 105 of the structure shown in FIG. 38 anddescribed above is mounted in position inside the rolling bearing in themanner which will now be described. After the sealing device 105 hasbeen assembled separate and independent of the rolling bearing, thesealing device 105 is press-fitted into the rolling bearing with theslinger 107 mounted on the inner race 101 and the core metal 108 fittedinside the outer race 102. During the press-fitting of the sealingdevice 105, a plurality of the sealing devices 105 stacked on a supporttable 114 as shown in FIG. 39 are delivered one by one into a chute bymeans of a handling unit of an automatic press-fitting machine and isthen picked up to be press-fitted in the rolling bearing.

[0011] However, since the sealing device 105 shown in FIG. 38 is of adesign integrated together with the rubber magnet 106, stacking on thesupport surface 114 (FIG. 39) the plural sealing devices 105 with thecore metal 108 held in contact with the support surface 114 and with theslinger 107, bonded by vulcanization with the corresponding rubbermagnet 106, positioned on one side of such core metal 108 remote fromthe support surface 114 results in contact of the rubber magnet 106 onthe slinger 107 in one of the sealing devices 105 with the core metal108 of the next adjacent sealing device 105 positioned immediately abovesuch one of the sealing devices 105. Considering that the rubber magnet106 exerts a magnetic force of attraction, the rubber magnet 106 in oneof the sealing devices 105 attracts the core metal 108 in the nextadjacent sealing device 105 positioned immediately above such one of thesealing devices 105 and, accordingly, a trouble often occurs indelivering the sealing devices 105 one by one by means of the handlingunit of the automatic press-fitting machine, thereby hampering a smoothautomatic press-fitting.

SUMMARY OF THE INVENTION

[0012] In view of the foregoing, the present invention has for itsobject to provide a sealing device for a wheel bearing effective toavoid any possible ingress of water through the engagement interface ofthe annular sealing plate to thereby increase the lifetime of the wheelbearing, substantially free from any possible problem associated withseparation and/or displacement of the annular sealing plate andeffective to secure a magnetic flux density.

[0013] The present invention has for its additional object to provide asealing device for a rolling bearing effective to avoid any possiblemagnetic attraction between the neighboring sealing devices when thelatter are stacked on a support table of the handling device so that thesealing devices can be transported into a chute one by one with notrouble to allow the individual sealing devices to be automaticallypress-fitted into the corresponding rolling bearings smoothly.

[0014] A wheel bearing according to a first aspect of the presentinvention includes an inner member, an outer member, a circular row ofrolling elements interposed between the inner and outer members, and asealing device for sealing an annular end space delimited between theinner and outer members. The sealing device includes:

[0015] first and second annular sealing plates secured respectively toone of the first and second members and the other thereof and disposedin face-to-face relation to each other;

[0016] each of the first and second annular sealing plates including acylindrical wall and a radial wall assembled together to represent agenerally L-shaped section;

[0017] the first annular sealing plate being mounted on one of the innerand outer members which is rotatable relative to the other of the innerand outer members, with the radial wall positioned on one side adjacentan exterior of the bearing;

[0018] a first elastic member mixed with a powder of magnetic particlesand bonded by vulcanization to the radial wall of the first annularsealing plate, the first elastic member being formed with a magnetizedportion in which opposite magnetic poles are formed alternately in adirection circumferentially thereof;

[0019] the second sealing plate including an elastic sealing member, theelastic sealing member being formed integrally with a side sealing lipslidingly engageable with the radial wall of the first annular sealingplate and a radial sealing lip slidingly engageable with the cylindricalwall of the first annular sealing plate;

[0020] the cylindrical wall of the second annular sealing plate beingspaced a slight radial gap from a free periphery of the radial wall ofthe first annular sealing plate; and

[0021] a second elastic material made of a material different from thatof the first elastic member bonded to the radial wall and interposed atan engagement of the first annular sealing plate with such one of thefirst and second members which is rotatable.

[0022] According to the above described construction, since the radialwall of the first annular sealing plate is bonded by vulcanization withthe first elastic member mixed with the powder of magnetic particles andmagnetized to opposite magnetic poles alternating in a circumferentialdirection thereof, a so-called encoder grid is formed by the magnetizedportion comprises of the first elastic member and rotation detection ispossible with a magnetic sensor confronting the magnetized portion.

[0023] With respect to the sealing between the inner and outer members,a seal is obtained by sliding engagement of the various sealing lipsprovided in the second annular sealing plate with the first annularplate and by a labyrinth seal formed by disposition of the radial freeperiphery or free edge of the radial wall of the first annular sealingplate spaced a slight distance from the cylindrical wall of the secondannular sealing plate to provide the radial gap.

[0024] As regards the engagement between the first annular sealing plateand the rotatable side member, the interposition of the second elasticmember is effective to fill up minute interstices resulting from theshape and the surface roughness of the engagement, to thereby increasethe effect of avoiding ingress of water. Since this second elasticmember is made of a material different from that for the first elasticmember mixed with the powder of magnetic particles to provide theencoder grid, a high sealability can be obtained by properly selectingthe material. For this reason, without allowing the greases to bedeteriorated in contact with water that has ingressed, the lifetime ofthe bearing can be increased. Also, since the second elastic memberprovides a sealing at the engagement, material for the first annularsealing plate is not limited and if the magnetic material is employedtherefor, the magnetic flux density of the encoder grid formed by theelastic member provided in the radial wall thereof can be increased bysuch magnetic material.

[0025] In a preferred embodiment according to the first aspect of thepresent invention, the second elastic member interposed at theengagement of the first annular sealing plate may be a coated layer ofrubber material applied to the first annular sealing plate.

[0026] If the second elastic member is comprised of the coated layer ofrubber material, any possible reduction of the engaging force at theengagement of the first annular sealing plate, which would otherwiseresult from because of the second elastic member, can be avoided. Forthis reason, while the sealability be increased, any possible separationand/or displacement of the first annular sealing plate can also beavoided.

[0027] In another preferred embodiment according to the first aspect ofthe present invention, the second elastic member interposed at theengagement of the first annular sealing plate may be a layer of paintmaterial applied to the first annular sealing plate and having a rustpreventive property.

[0028] Even though the second elastic member is a layer of paintmaterial, that is, a paint layer, any possible reduction of the force ofengagement at the engagement of the first annular sealing plate, whichwould otherwise result from because of the second elastic member, can beavoided and, while the sealability be increased, any possible separationand/or displacement of the first annular sealing place can also beavoided. Also, since the paint material is of a kind having a rustpreventive property, the first annular sealing plate can exhibit a rustproof and, therefore, the magnetic material can be selected for thefirst annular sealing plate with no possibility of being rusted

[0029] The paint material referred to above may be a polyethylene rubberpaint.

[0030] In a further preferred embodiment according to the first aspectof the present invention, the second elastic member interposed at theengagement of the first annular sealing plate may be a layer of adhesivematerial applied to the first annular sealing plate and having a rustpreventive property. The adhesive material referred to above may be aresinous room temperature setting adhesive having an anaerobic property.

[0031] Where the adhesive layer is interposed, the adhesive materialeffectively fill up minute interstices resulting from the shape and thesurface roughness of the engagement, to thereby increase the force ofengagement of the annular sealing plate to thereby increase thesealability. The resinous room temperature setting adhesive having ananaerobic property has a low cure rate when in contact with air, but canrelatively quickly cure at room temperatures when applied to theengagement surface 18 where air is barely present. Accordingly, the sizeof a play between the first annular sealing plate and the inner or outermember engaged therewith for interference fit can be minimized toincrease the assemblage.

[0032] In a still further preferred embodiment according to the firstaspect of the present invention, the surface of the first annularsealing plate which forms the engagement preferably has a surfaceroughness not greater than Rmax 3.0, where Rmax represents a maximumheight of surface profile. The surface roughness may be chosen Rmax0.5-2.2.

[0033] The more coarse the surface of the annular sealing plate, thehigher the bonding strength of the second elastic member in the form ofa thin film. However, if the surface of the annular sealing plate is toocoarse, the dimensional precision of the surface of the annular sealingplate is lowered. Although hitherto the surface of the first annularsealing plate which forms the engagement has been chosen to be of Rmaxgreater than 3.0 and not greater than 7.5, selection of the surfaceroughness not greater than Rmax 3.0 is effective to maintain thedimensional precision of the inner diameter of the second elastic memberwhile securing a sufficient bonding strength of the second elasticmember.

[0034] In a still further preferred embodiment according to the firstaspect of the present invention, the inner member may have an outerperipheral surface formed with an annular groove, and the second elasticmember of the different material is a ring-shaped rubber member, and thefirst annular sealing plate is mounted on the inner member through thering-shaped rubber member. When the annular groove is formed in theouter peripheral surface of the inner member, it is possible to causethe annular groove to trap water when the latter ingresses. Also, thesealability can be increased by the use of the ring-shaped rubber membermounted in the annular groove.

[0035] In a still further preferred embodiment according to the firstaspect of the present invention, an annular joint between thecylindrical wall and the radial wall of the first sealing plate may beprovided with a folded portion that extends radially inwardly from theradial wall and joined to the cylindrical wall after having been turnedbackwards and, on the other hand, an annular depression may be formed onan outer peripheral end surface of the inner member by radially inwardlydepressing to provide a reduced diameter portion. In this case, thefirst annular sealing plate is mounted on the inner member with thefolded portion positioned within the annular depression, and the secondelastic member of the different material is a ring-shaped rubber memberthat is interposed between an annular side face of the annulardepression and the folded portion.

[0036] When the first annular sealing plate is mounted on the innermember with the folded portion positioned within the annular depressionin the manner described above, the passage for the flow of waterrepresents a tortuous configuration, making it difficult for the waterto ingress into the interior of the bearing. Also, the interposition ofthe ring-shaped rubber member between an annular side face of theannular depression and the folded portion is effective to provide asufficient sealability. In addition, the provision of the folded portionis effective not only to increase the rigidity of the first annularsealing plate itself, but also the press work to form the first annularsealing plate can be performed with little elastic region (spring back)of the material left therein, and any possible deformation of the firstannular sealing plate which would otherwise occur when heated to anelevated temperature during a subsequent heat treatment and/orvulcanization of the rubber material for the elastic member canadvantageously be avoided. For this reason, the shape precision of thefirst annular sealing plate can be increased and the sealability due toengagement can further be increased.

[0037] In a still further preferred embodiment according to the firstaspect of the present invention, an annular depression may be formed onan outer peripheral end surface of the inner member by radially inwardlydepressing to provide a reduced diameter portion, and the first annularsealing plate may be mounted on the annular depression with thecylindrical wall thereof engaged with an outer peripheral surface of theannular depression. In this case, the second elastic member of thedifferent material is preferably a ring-shaped rubber member that isinterposed between an axial free end of the cylindrical wall of thefirst annular sealing plate and an annular side face of the annulardepression.

[0038] In this structure, by allowing the second elastic member, in theform of the ring-shaped rubber member, to elastically contact theannular side face of the annular depression, even though dusts ingressthrough the engagement, further ingress thereof into the interior of thebearing can be prevented by the second elastic member. Also, since amajor portion of the cylindrical wall of the first annular sealing plateis engaged directly on the inner member, a high force of engagement canbe obtained. Thus, this structure is excellent in that any possibleseparation and/or displacement of the sealing plate can advantageouslybe prevented.

[0039] In a still further preferred embodiment according to the firstaspect of the present invention, the cylindrical wall of the firstannular sealing plate may be formed with a stop member which is in turnengaged in an annular groove defined on the outer peripheral surface ofthe inner member. By allowing the stop member to engage in the annulargroove, any possible axial displacement of the first annular sealingplate can be avoided. For this reason, while the second elastic memberis interposed at the engagement of the first annular sealing plate, anypossible separation and/or displacement can be assuredly prevented.

[0040] The stop member referred to above may be comprised of a bent endformed at an axial free end of the cylindrical wall of the first annularsealing plate. If the stop member is represented by the bent end of theaxial free end portion of the cylindrical wall of the first annularsealing plate, it can easily be formed. Also, since the stop member isprovided at the axial free end of the cylindrical wall, the stop memberwill not provide any obstruction and the cylindrical wall can easily bemounted onto the inner member.

[0041] Alternatively, the stop member may be comprised of a plurality ofprotuberances formed on the cylindrical wall of the first annularsealing plate at a position generally intermediate of an axial length ofthe cylindrical wall and spaced a distance from each other in adirection circumferentially of the cylindrical wall of the first annularsealing plate. If the stop member is in the form of the pluralprotuberances, the stop member can easily be formed and formation of thestop member is effective to avoid any possible reduction of the area ofsurface of engagement.

[0042] Again alternatively, the stop member may be comprised of anannular projection formed in the cylindrical wall of the first annularsealing plate at a location generally intermediate of an axial length ofthe cylindrical wall and extending circumferentially of the cylindricalwall. Even when the stop member is in the form of the annularprojection, the stop member can easily be formed. Also, when the stopmember is in the form of the annular projection, the effect ofpreventing the first annular sealing plate from being displaced is high.

[0043] According to the second aspect of the present invention, there isprovided a wheel bearing including an inner member, an outer member, acircular row of rolling elements interposed between the inner and outermembers, and a sealing device for sealing an annular end space delimitedbetween the inner and outer members. This sealing device includes:

[0044] first and second annular sealing plates secured respectively toone of the first and second members and the other thereof, and disposedin face-to-face relation to each other;

[0045] each of the first and second annular sealing plates including acylindrical wall and a radial wall assembled together to represent agenerally L-shaped section;

[0046] the first annular sealing plate being mounted on one of the innerand outer members which is rotatable relative to the other of the innerand outer members, with the radial wall positioned on one side adjacentan exterior of the bearing;

[0047] a first elastic member mixed with a powder of magnetic particlesand bonded by vulcanization to the radial wall of the first annularsealing plate, the first elastic member being formed with a magnetizedportion in which opposite magnetic poles are formed alternately in adirection circumferentially thereof;

[0048] the second sealing plate including an elastic sealing member, theelastic sealing member being formed integrally with a side sealing lipslidingly engageable with the radial wall of the first annular sealingplate and a radial sealing lip slidingly engageable with at least one ofthe cylindrical wall of the first annular sealing plate and the one ofthe inner and outer members which is rotatable;

[0049] the cylindrical wall of the second annular sealing plate beingspaced a slight radial gap from a free periphery of the radial wall ofthe first annular sealing plate; and

[0050] the elastic sealing member having an elastic projection formedtherewith so as to extend outwardly therefrom, the elastic projectionbeing elastically engaged with a connecting member that is held incontact with an annular axial end face of the inner member.

[0051] In the case of this structure, similarly to the first aspect ofthe present invention, a so-called encoder grid is formed by themagnetized portion, and an effective sealing is attained by the sealinglips and a labyrinth seal between the first and second annular sealingplates. Also, by allowing the elastic projection protruding from theelastic member forming the magnetized portion to elastically engage theconnecting member that is held in contact with the annular axial endface of the inner member, any possible ingress of water and/or dustsinto the interior of the bearing can be prevented. Since the firstannular sealing plate is engaged directly with the inner member with noelastic member intervening therebetween, there is no problem associatedwith reduction in the force of engagement.

[0052] The connecting member referred to above may be a constant speeduniversal coupling having a shoulder that is held in contact with theannular axial end face of the inner member.

[0053] Alternatively, the connecting member may be a crimped portion ofa barrel hub which is crimpled radially outwardly to confront an axialend of a separate inner race then held in abutment with one end of thebarrel hub. In this case, if the crimped portion is utilized as a membercontactable with the elastic projection integral with the elasticmember, the elastic projection need not be formed in a relatively largesize and the elastic contact with the elastic projection is effective toprovide a sealing capability.

[0054] In any one of the foregoing preferred embodiments according tothe second aspect of the present invention, the elastic projection maybe of a type elastically held in contact with an outer peripheralsurface of the connecting member. Contact of the elastic projection withthe outer peripheral surface of the connecting member does not require adedicated portions on the connecting member to be prepared for contactwith the elastic projection and the contact of the elastic projectioncan be accomplished, thereby enabling the sealing capability to beachieved with a simplified structure.

[0055] In any one of the foregoing preferred embodiments according tothe second aspect of the present invention, the elastic projection maybe elastically held in contact with a side face of the connectingmember. Where the elastic projection is held in contact with the sideface of the connecting member, the elastic member can be standardizedwithout being restricted by the outer diameter dimension of theconnecting member.

[0056] In any one of the foregoing preferred embodiments according tothe second aspect of the present invention, the radial sealing lip ofthe second sealing plate may be slidingly engaged with the inner member.Sliding engagement of the radial sealing lip of the second sealing platewith the inner member is effective to further increase the sealability.

[0057] Also, in accordance with the third aspect of the presentinvention, there is provided a wheel bearing including an inner member,an outer member, a circular row of rolling elements interposed betweenthe inner and outer members, and a sealing device for sealing an annularend space delimited between the inner and outer members. The sealingdevice employed in the wheel bearing according to the third aspect ofthe present invention includes:

[0058] first and second annular sealing plates secured respectively toone of the first and second members and the other thereof, and disposedin face-to-face relation to each other;

[0059] each of the first and second annular sealing plates including acylindrical wall and a radial wall assembled together to represent agenerally L-shaped section;

[0060] the first annular sealing plate being mounted on one of the innerand outer members which is rotatable relative to the other of the innerand outer members, with the radial wall positioned on one side adjacentan exterior of the bearing;

[0061] a first elastic member mixed with a powder of magnetic particlesand bonded by vulcanization to the radial wall of the first annularsealing plate, the first elastic member being formed with a magnetizedportion in which opposite magnetic poles are formed alternately in adirection circumferentially thereof;

[0062] the second sealing plate including an elastic sealing member, theelastic sealing member being formed integrally with a side sealing lipslidingly engageable with the radial wall of the first annular sealingplate and a radial sealing lip slidingly engageable with the cylindricalwall of the first annular sealing plate;

[0063] the cylindrical wall of the second annular sealing plate beingspaced a slight radial gap from a free periphery of the radial wall ofthe first annular sealing plate; and

[0064] of the first and second annular sealing plates, at lest the firstannular sealing plate being prepared from a steel plate made of amagnetic material, the steel plate having a surface formed with ametallic layer made of metal having a Yong's modulus of elasticity thatis lower than that for the one of the first and second members which isrotatable.

[0065] Again, according to the structure described above, a so-calledencoder grid is formed by the magnetized portion, and an effectivesealing is attained by the sealing lips and a labyrinth seal between thefirst and second annular sealing plates.

[0066] As regards the engagement between the first annular sealing plateand one of the inner and outer members which is on a rotatable side,although minute interstices resulting from the shape and the surfaceroughness are formed, surface indents forming the minute interstices canadvantageously be filled by a soft metal forming the metallic layersince the metallic layer of a metal having a Young's modulus ofelasticity smaller than that of the rotatable side member is formed onthe surface of the first annular sealing plate, thereby increasing thesealability. Accordingly, without allowing the greases to bedeteriorated in contact with water that has ingressed, the lifetime ofthe bearing can be increased. Also, since a steel plate is employed asmaterial for the first annular sealing plate, the magnetic flux densityof the encoder grid can be increased. Since the metallic layer on thesurface of the steel plate for the first annular sealing plate is thin,the magnetic flux density will not be little affected even though it isnon-magnetic.

[0067] In a preferred embodiment according to the third aspect of thepresent invention, the metallic layer may be a metal plated layer. Ifthe metallic layer is comprised of a metal plated layer, the metalliclayer can easily be formed. Also, the metal having the low Young'smodulus of elasticity may be selected from the group consisting of zinc,tin, gold, silver and copper.

[0068] In another preferred embodiment according to the third aspect ofthe present invention, the metallic layer may have a thickness withinthe range of 5 to 30 μm.

[0069] If the surface roughness of the engagement surface of the memberon which the first annular sealing plate is mounted is about Rmax 3.0(or Ra 0.63, where Ra represents a center line average height of surfaceprofile), in order for the resultant minute surface irregularities to befilled up, the thickness of the metallic layer has to be at least notsmaller than 5 μm. On the other hand, even if this thickness is chosento be not smaller than 30 μm, effects brought about thereby remain thesame and, conversely, the evenness or flatness will be adverselyaffected, requiring an increased length of time to form the metalliclayer together with increase of the cost. For this reason, the thicknessof the metallic layer is preferred to be within the above mentionedrange. To form the metallic layer of a thickness within the range of 5to 30 μm, it is effective where the metallic layer is comprised of ametal plated layer.

[0070] In a further preferred embodiment of the present inventionaccording to the third aspect of the present invention, a surface of thefirst annular sealing plate which forms the engagement may have asurface roughness not greater than Rmax 3.0, more preferably within therange of Rmax 0.5 to 2.2.

[0071] While such an annular sealing plate has hitherto been consideredhaving a surface roughness of Rmax greater than 3.0 and not greater 7.5,increase of the degree of surface evenness or flatness is effective toallow the metallic layer to fill up the surface irregularities broughtabout thereby.

[0072] In a still further preferred embodiment of the present inventionaccording to the third aspect of the present invention, a surface of theengagement of one of the first and second members, which is rotatable,with the first annular sealing plate may be formed as a ground surfacewhich has been plunge cut.

[0073] With the plunge cutting, the raceway for the rolling elements inthe rotatable member and the engagement surface are simultaneouslyformed by machining or grinding and, therefore, any misalignmenttherebetween can advantageously be avoided. In other words, if they areseparately machined or ground, not only does a misalignment between theengagement surface, which eventually provides a sealing surface, and theraceway occur, but also there is a high risk of ingress of dusts whenthe engagement surface is machined or grinded without a sensor forsensing machined surface rendering the machined surface spiral. Sincethe plunge cutting is a technique in which a grinding wheel is appliedat right angles to the work to be ground, the above discussed problemscan advantageously eliminated.

[0074] Where the engagement surface of the rotatable member where theannular sealing plate is engaged therewith is defined by the plunge cutsurface, it is desirable for the engagement surface to be finished to asurface roughness not greater than Rmax 3.0. This engagement surface aswell is preferred to be within the range of Rmax 0.5 to 2.2. Even if thedegree of the surface evenness of the engagement surface is increased,the function of the metallic layer to fill up the surface irregularitiesresulting from the surface roughness can be enhanced.

[0075] Again, in accordance with the fourth aspect of the presentinvention, there is provided a wheel bearing including an inner member,an outer member, a circular row of rolling elements interposed betweenthe inner and outer members, and a sealing device for sealing an annularend space delimited between the inner and outer members. This sealingdevice used therein includes:

[0076] first and second annular sealing plates secured respectively toone of the first and second members and the other thereof, and disposedin face-to-face relation to each other;

[0077] each of the first and second annular sealing plates including acylindrical wall and a radial wall assembled together to represent agenerally L-shaped section;

[0078] the first annular sealing plate being mounted on one of the innerand outer members which is rotatable relative to the other of the innerand outer members, with the radial wall positioned on one side adjacentan exterior of the bearing;

[0079] a first elastic member mixed with a powder of magnetic particlesand bonded by vulcanization to the radial wall of the first annularsealing plate, the first elastic member being formed with a magnetizedportion in which opposite magnetic poles are formed alternately in adirection circumferentially thereof;

[0080] the cylindrical wall of the second annular sealing plate beingspaced a slight radial gap from a free periphery of the radial wall ofthe first annular sealing plate; and

[0081] the second sealing plate including an elastic sealing member, theelastic sealing member being formed integrally with a side sealing lipslidingly engageable with the radial wall of the first annular sealingplate and a radial sealing lip slidingly engageable with an outerperipheral surface of the one of the inner and outer members, which isrotatable, and adjacent an engagement surface of the first annularsealing plate with such one member.

[0082] With this structure as described above, a so-called encoder gridis formed by the magnetized portion, and an effective sealing isattained by the sealing lips and a labyrinth seal between the first andsecond annular sealing plates. Since of the elastic sealing lips, theradial sealing lip is held in sliding engagement with the outerperipheral surface adjacent the engagement of the rotatable side memberwith the annular sealing plate, even though water ingresses across theengagement between the first annular sealing plate and the rotatableside member, further ingress of the water into the interior of thebearing can be prevented by the sliding engagement of the radial sealinglip. For this reason, there is no possibility of the grease beingdegraded in contact with water and the lifetime of the bearing can beincreased. Also, since the sealability can be secured by the radialsealing lip in this way, the material for the first annular sealingplate is not limited and any suitable magnetic material can be employed,allowing the magnetic flux density of the encoder grid, defined by theelastic member provided on the radial wall, to be increased.

[0083] In a preferred embodiment according to the fourth aspect of thepresent invention, an annular depression of a depth corresponding to athickness of the first annular sealing plate is formed on the rotatableside, and the cylindrical wall of the first annular sealing plate ispress-fitted around an outer peripheral surface of the annulardepression. If the annular depression is provided and the first annularsealing plate is mounted thereon, any possible axial displacement of thefirst annular sealing plate towards the interior of the bearing can beprevented and, therefore, the axial position of the first annularsealing plate is limited, thereby securing a proper interference for theelastic side sealing lip. The annular depression referred to above has asmall depth corresponding to the thickness of the cylindrical wall ofthe annular sealing plate, there is no problem associated with reductionin strength of the rotatable side member resulting from the formation ofthe annular depression and also with increase in size of the firstannular sealing plate and also no problem associated with insufficientengagement which would otherwise result from an insufficient depth ofthe annular depression.

[0084] In another preferred embodiment according to the fourth aspect ofthe present invention, the radial sealing lip of the second sealingplate may be inclined so as to extend outwardly of the bearing. Wherethe radial sealing lip is inclined so as to extend outwardly of thebearing, as compared with the radial sealing lip inclined so as toextend in a reverse direction, that is, inwardly of the bearing, theeffect of preventing water and dusts from ingressing exteriorly into theinterior of the bearing can be increased.

[0085] In a further preferred embodiment according to the fourth aspectof the present invention, the side sealing lip of the second annularsealing plate may be provided at two locations spaced radially. The sidesealing lip functions to prevent any possible flow of water from theoutside of the bearing into the interior of the bearing and, therefore,the provision of this side sealing lip at two locations spaced radiallyinwardly and outwardly is effective to enhance the effect of preventingwater ingress into the interior of the bearing.

[0086] In a still further preferred embodiment according to the fourthaspect of the present invention, the first annular sealing plate may bemade of a ferrite stainless steel. Considering that the ferritestainless steel is a ferromagnetic material, the use thereof as materialfor the first annular sealing plate is effective to increase themagnetic flux density of the elastic member defining the encoder grid.

[0087] In a still further preferred embodiment of the present inventionaccording to the fourth aspect of the present invention, at least one ofa free peripheral edges of the radial wall of the first annular sealingplate and the cylindrical wall of the second sealing plate may beprovided with an overhang portion defined by a portion of the elasticmember integrated with the annular sealing plate, in which case amaximum diameter portion of the free peripheral edge of the radial wallof the first annular sealing plate including this overhang portion has adiameter greater than a minimum diameter portion of an axial free end ofthe cylindrical wall of the second annular sealing plate and ispositioned inwardly of the bearing from the minimum diameter portion.

[0088] According to this embodiment, since the radial sealing lip on thesecond annular sealing plate is held in sliding contact with the outerperipheral surface of the rotatable side member, and not held in slidingcontact with the cylindrical wall of the first annular sealing plate,unless a countermeasure is taken, the first and second annular sealingplates will separate from each other while the sealing device has notyet been assembled into the bearing. For this reason, transportation andan assemblage of the sealing device into the bearing are complicated,accompanied by increase of manufacturing steps. In contrast thereto,since the overhang portion is engageable with the free end of thecylindrical wall of the second annular sealing plate in the axialdirection, the possible separation between the first and second annularsealing plates can be prevented in a condition having not yet beenassembled, and they can be dealt with as a single component part. Also,since the first and second annular sealing plates are engaged with eachother in a manner that is unseparable from each other by means of theoverhang portion integral with the elastic member, they can be assembledtogether or dismantled from each other by virtue of elastic deformationof the overhang portion. Also, the provision of the overhang portionrenders the gap, forming the labyrinth seal, to represent a generallytortuous shape, resulting in increase of the sealability.

[0089] The present invention provides a sealing device that may beincluded in the wheel bearing according to any one of the first tofourth aspects of the present invention. In this sealing device, one ofthe first and second annular sealing plates which is on a fixed side maybe made of a metal and such fixed side annular sealing plate or theelastic sealing member mounted thereon may be formed with a projectionprotruding inwardly of the wheel bearing, which projection is formed soas to be continuous or discontinuous.

[0090] It is to be noted that the projections referred to above may beformed integrally with the annular sealing plate.

[0091] According to the sealing device of the structure described above,when the sealing device is to be press-fitted to the bearing, aplurality of the sealing devices of an identical structure are placed ona support table, a space corresponding to the amount of protrusion ofthe annular projection protruding from the outer side face of theannular sealing plate fixed to the fixed member of the bearing and,therefore, the magnetic force of attraction acting to attract one of thesealing devices immediately above the magnetized portion of the other ofthe sealing devices stacked immediately above the magnetized portionthereof is weakened. Consequently, the neighboring sealing devicesstacked on the support table will not be magnetically attracted witheach other and, therefore, the sealing devices can advantageously betransported towards a chute by the handling unit of the automaticpress-fitting machine one at a time and are then successively assembledinto the respective bearings one at a time.

[0092] It is to be noted that in place of the first elastic memberincluding the magnetized portion, the magnetized portion may be formedon the radial wall of the annular sealing plate, that is on therotatable side, by directly magnetizing such radial wall of such annularsealing plate.

[0093] The present invention also provides a sealing device that may beincluded in the wheel bearing according to any one of the first tofourth aspects of the present invention. In this sealing device, one ofthe first and second annular sealing plates which is on a fixed side maybe made of a metallic non-magnetic material.

[0094] According to the sealing device of the structure described above,the magnetic force of attraction emanating from the magnetized portiondoes not act on the annular sealing plate formed of the non-magneticmaterial and mounted on the fixed member of one of the sealing devicespositioned above the other of the sealing devices. Consequently, theneighboring sealing devices stacked on the support table will not bemagnetically attracted with each other.

[0095] The non-magnetic material is preferably in the form of anaustenite stainless steel because it has a corrosion resistanceeffective to suppress rusting. Of the stainless steels available, SUS304 is preferred because it is mass-produced and exhibits a requiredstrength.

BRIEF DESCRIPTION OF THE DRAWINGS

[0096] In any event, the present invention will become more clearlyunderstood from the following description of preferred embodimentsthereof, when taken in conjunction with the accompanying drawings.However, the embodiments and the drawings are given only for the purposeof illustration and explanation, and are not to be taken as limiting thescope of the present invention in any way whatsoever, which scope is tobe determined by the appended claims. In the accompanying drawings, likereference numerals are used to denote like parts throughout the severalviews, and:

[0097]FIG. 1 is a fragmentary sectional view of a wheel bearingaccording to a first preferred embodiment in the first aspect of thepresent invention;

[0098]FIG. 2 is a fragmentary front elevational view of an elasticmaterial eventually forming an encoder grid employed in the wheelbearing shown in FIG. 1;

[0099]FIG. 3 is a longitudinal sectional view of the wheel bearing shownin FIG. 1;

[0100]FIG. 4 is a longitudinal sectional view of modified form ofelastic sealing member in the wheel bearing of FIG. 1;

[0101]FIGS. 5A and 5B are fragmentary sectional views of the wheelbearing according to a second preferred embodiment in the first aspectof the present invention;

[0102]FIG. 6 is a fragmentary sectional view of the wheel bearingaccording to a third preferred embodiment in the first aspect of thepresent invention;

[0103]FIG. 7 is a fragmentary sectional view of the wheel bearingaccording to a fourth preferred embodiment in the first aspect of thepresent invention;

[0104]FIG. 8 is a fragmentary sectional view of the wheel bearingaccording to a fifth preferred embodiment in the first aspect of thepresent invention;

[0105]FIG. 9 is a fragmentary sectional view of the wheel bearingaccording to a sixth preferred embodiment in the first aspect of thepresent invention;

[0106]FIG. 10 a fragmentary sectional view of the wheel bearingaccording to a seventh preferred embodiment in the first aspect of thepresent invention;

[0107]FIG. 11 is an explanatory diagram showing the manner of assemblingthe first annular sealing plate used therein;

[0108]FIG. 12 is a fragmentary sectional view of the wheel bearingaccording to an eighth preferred embodiment in the first aspect of thepresent invention;

[0109]FIG. 13 is a fragmentary perspective view of the first annularsealing plate used therein;

[0110]FIG. 14 is a fragmentary perspective view of a modified form ofthe first annular sealing plate used therein;

[0111]FIG. 15 is a fragmentary sectional view of the wheel bearingaccording to a first preferred embodiment in the second aspect of thepresent invention;

[0112]FIG. 16 is a fragmentary sectional view of the wheel bearingaccording to a second preferred embodiment in the second aspect of thepresent invention;

[0113]FIG. 17 is a fragmentary sectional view of the wheel bearingaccording to a third preferred embodiment in the second aspect of thepresent invention;

[0114]FIG. 18 is a fragmentary sectional view of the wheel bearingaccording to a fourth preferred embodiment in the second aspect of thepresent invention;

[0115]FIG. 19 is a fragmentary sectional view of the wheel bearingaccording to a fifth preferred embodiment in the second aspect of thepresent invention;

[0116]FIG. 20 is a fragmentary sectional view of a sealing device forthe wheel bearing according to a sixth preferred embodiment in thesecond aspect of the present invention;

[0117]FIG. 21A is a fragmentary sectional view of the wheel bearingaccording to a preferred embodiment in the third aspect of the presentinvention;

[0118]FIG. 21B is a sectional view, on an enlarged scale, showing thesealing device employed in the wheel bearing shown in FIG. 21A;

[0119]FIG. 22 is a sectional view showing a modified form of the sealingdevice according to the third aspect of the present invention;

[0120]FIG. 23 is a fragmentary sectional view of the wheel bearingaccording to a first preferred embodiment in the fourth aspect of thepresent invention;

[0121]FIG. 24 is a fragmentary sectional view of the wheel bearingaccording to a second preferred embodiment in the fourth aspect of thepresent invention;

[0122]FIG. 25 is a fragmentary sectional view of the wheel bearingaccording to a third preferred embodiment in the fourth aspect of thepresent invention;

[0123]FIG. 26 is a fragmentary sectional view of the wheel bearingaccording to a fourth preferred embodiment in the fourth aspect of thepresent invention;

[0124]FIG. 27 is a fragmentary sectional view of the wheel bearingaccording to a fifth preferred embodiment in the fourth aspect of thepresent invention;

[0125]FIG. 28 is a fragmentary sectional view of the wheel bearingaccording to a six preferred embodiment in the fourth aspect of thepresent invention;

[0126]FIG. 29 is a fragmentary sectional view of the wheel bearingaccording to a seventh preferred embodiment in the fourth aspect of thepresent invention;

[0127]FIG. 30 is an explanatory diagram showing an example of machiningan inner race;

[0128]FIG. 31 is a fragmentary sectional view of the sealing deviceaccording to a first preferred embodiment in the fifth aspect of thepresent embodiment;

[0129]FIG. 32 is a fragmentary sectional view of the sealing deviceaccording to a second preferred embodiment in the fifth aspect of thepresent invention;

[0130]FIG. 33 is a fragmentary sectional view of the sealing deviceaccording to a third preferred embodiment in the fifth aspect of thepresent invention;

[0131]FIG. 34 is a fragmentary sectional view of the sealing deviceaccording to a fourth preferred embodiment in the fifth aspect of thepresent invention;

[0132]FIG. 35 is a sectional view showing the manner in which thesealing devices according to the embodiment shown in FIG. 31 are stackedone above the other on a support table;

[0133]FIG. 36A is a schematic plan view showing an example of aprojection employed in the sealing device shown in FIG. 31;

[0134]FIG. 36B is a schematic plan view of a modified form of theprojection;

[0135]FIG. 37 is a fragmentary sectional view of one prior art sealingdevice employed in the wheel bearing;

[0136]FIG. 38 is a fragmentary sectional view of another prior artsealing device employed in a rolling bearing; and

[0137]FIG. 39 is an explanatory diagram showing the manner in which theprior art sealing devices are stacked one above the other on the supporttable.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0138] Preferred embodiments of the present invention will now bedescribed. Referring first to FIG. 1, a wheel bearing shown thereinincludes an inner and outer members 1 and 2 rotatable relative to eachother, a circular row of rolling elements 3 interposed rollingly betweenthe first and second members 1 and 2, and a sealing device 5 foroperatively sealing an annular end space delimited between the inner andouter members 1 and 2. Each of the inner and outer members 1 and 2 has araceway 1 a or 2 a defined therein in the form of a generallysemicircular sectioned groove. The inner and outer members 1 and 2rollingly support the circular row of the rolling elements 3 and arepositioned radially inwardly and outwardly of the circular row of therolling element for rotation relative to each other. The inner and outermembers 1 and 2 may respectively be inner and outer races of a rollingbearing or bearing inner and outer races combined together with separatecomponent parts. Alternatively, the inner member 1 may be a part of arotary shaft. The rolling elements 3 may be balls or rollers, but in theillustrated embodiment the rolling elements 3 are employed in the formof balls.

[0139] An example of the entire structure of the wheel bearing is shownin FIG. 3. The wheel bearing shown therein may be in the form of adouble row rolling bearing or, specifically, a double row angularbearing and includes a bearing inner race comprised of a barrel hub 6and a separate inner race 1A mounted externally on one end of the barrelhub 6. The barrel hub 6 and the separate inner race 1A are formed withrespective raceways for rollingly accommodating respective circular rowsof rolling elements. The separate inner race 1A serves as the innermember 1 in the example shown in FIG. 1. The barrel hub 6 is coupledwith one end (for example, an outer race) of a constant speed universalcoupling 7 while a wheel (not shown) is bolted to a hub portion 6 a ofthe barrel hub 6 by means of a plurality of bolts 8. The constant speeduniversal coupling 7 has the opposite end (for example, an inner race)coupled with a drive shaft. The outer member 2 is constituted by abearing outer race having a flange 2 b and is fitted to a housing 10including a knuckle or the like. This outer member 2 is of a type havingraceways defined therein for the respective circular rows of the rollingelements 3. The rolling elements 3 of each circular row are retained inposition by a retainer 4. An annular space delimited between the innerand outer members 1 and 2 has one end adjacent a generally intermediateportion of the wheel axle sealed by the sealing device 5. An annularspace delimited by the outer member 2 and the barrel hub 6 remote fromthe sealing device 5 is sealed by a different sealing device 13.

[0140] The sealing device 5 includes, as shown in FIGS. 1 and 2, firstand second annular sealing plates 11 and 12 fitted to the inner andouter members 1 and 2, respectively. The first and second annularsealing plates 11 and 12 are mounted in position to the inner and outermembers 1 and 2 under interference fit, respectively, in face-to-facerelation with each other. Each of the first and second annular sealingplates 11 and 12 is of a generally L-shaped section including acylindrical wall 11 a or 12 a and a radial wall 11 b or 12 b.

[0141] Of the first and second annular sealing plates 11 and 12, thefirst annular sealing plate 11 is press-fitted on an outer peripheralsurface of the inner member 1 which serves as a rotatable member and asa slinger. The radial wall 11 b of the first annular sealing plate 1 ispositioned axially outwardly of the bearing or on one side adjacent anexterior of the bearing and is bonded by vulcanization with an annularelastic member 14 mixed with a powder of magnetic particles. Thisannular elastic member 14 serves as an encoder grid and is formed with aplurality of pairs of magnetically opposite N and S poles alternating ina circular row over the circumference thereof as shown in FIG. 2. Thus,this annular elastic member 14 may be regarded as an annular rubbermagnet. The N and S pole regions are arranged alternately at apredetermined pitch p as measured along the pitch circle PCD lying onthe shape of a circle concentric with the circular row of the N and Spole regions. Positioned in face-to-face relation with the annularelastic member 14 serving as the encoder grid is a magnetic sensor 15,as shown in FIG. 1, that is cooperable with the annular elastic member14 to constitute a rotary encoder for detecting the speed of rotation ofthe wheel.

[0142] The second annular sealing plate 12 is integrated with a sidesealing lip 16 a, slidingly engaged with the radial wall 11 b of thefirst annular sealing plate 11, and radial sealing lips 16 b and 16 cslidingly engaged with the cylindrical wall 11 a of the first annularsealing plate 11. These sealing lips 16 a to 16 c form respective partsof an elastic sealing member 16 bonded by vulcanization to the secondannular sealing plate 12. The number of elastic sealing lips althoughshown as three 16 a to 16 c in the illustrated embodiment may bearbitrarily chosen, but in the illustrated embodiment in FIG. 1, the tworadial sealing lips 16 c and 16 b are employed and positioned axiallyoutwardly and inwardly of the bearing, respectively. The outer radialsealing lip 16 b may, if desired, replaced with a side sealing lip asshown in FIG. 4 or dispensed with.

[0143] The cylindrical wall 12 a of the second annular sealing plate 12and a free periphery of the radial wall 11 b of the first annularsealing plate 11 confront with each other and are spaced a slight radialdistance to form an annular gap which defines a labyrinth seal 17.

[0144] The first annular sealing plate 11 is preferably made of a steelplate having a magnetic property such as a ferromagnetic property.Examples of such magnetic steel plate include a stainless steel of aferrite system (for example, SUS 430 as stipulated in the JapaneseIndustrial Standards) and a rolled steel plate that has been preserved,i.e., subjected to a rust preventive treatment. On the other hand, thesecond annular sealing plate 12 is preferably made of stainless steel,for example, a stainless steel plate of an austenite system which isnon-magnetic (for example, SUS 304) or a rolled steel plate that hasbeen subjected to a rust preventive treatment. By way of example, thefirst annular sealing plate 11 and the second annular sealing plate 12may be prepared from the ferrite stainless steel plate and the austenitestainless plate, respectively.

[0145] An elastic member 20 made of an elastic material different fromthat for the elastic member 14 is bonded by vulcanization to anengagement surface 18 of the first annular sealing plate 11, which isheld in contact with an outer peripheral surface of the inner member 1so as to intervene between the cylindrical wall 11 a of the firstannular sealing plate 11 and that outer peripheral surface of the innermember 1. This elastic member 20 may be made of a rubber material in theform of a thin film or a ring, or any other suitable elastic material.Various specific configurations of the elastic member 20 will now bedescribed.

[0146] Where the elastic member 20 is in the form of a thin film, itwill be described together with a process of making the same. When arubber material is to be bonded by vulcanization to a annular sealingplate, it is a general practice to apply a thermosetting bondingmaterial to the annular sealing plate, followed by vulcanization of therubber material so as to stick to the annular sealing plate. However,where the rubber member 14 that eventually forms the encoder grid andthe rubber member 20 that eventually forms a packing dissimilar to therubber member 14 are to be formed, these dissimilar rubber materialscannot be injected simultaneously into a mold assembly for molding.

[0147] In view of the foregoing, by way of example, the elastic member20 may be formed on the engagement surface 18 of the first annularsealing plate 11 by, for example, spraying a rubber material only to theengagement surface 18 to form a rubber coat after a magnetic rubbermaterial has been bonded by vulcanization with the use of a bondingagent 21 to the first annular sealing plate 11 as shown in FIG. 5A,

[0148] The elastic member 20 in the form of a thin film may be a layerof resinous paint. By way of example, after the magnetic rubber materialhas been bonded by vulcanization with the use of a bonding agent 21 tothe first annular sealing plate 11 as is the case with the example shownin FIG. 5B, a resinous paint may be sprayed only to the engagementsurface 18 to form the elastic member 20. The resinous paint may be arubber paint of a polyethylene system and may be painted to a filmthickness of, for example, 20 μm.

[0149] The elastic member 20 in the form of a thin film may be a layerof a bonding material. Even in this case, as is the case with theexample shown in FIGS. 5A and 5B, after the magnetic rubber is bonded byvulcanization with the use of a bonding agent 21 to form the elasticmember 14, a bonding material for the thin film may be sprayed only tothe engagement surface 18 to form the elastic member 20. This bondingmaterial has a rust proof and is preferably employed in the form of aresinous bonding material more preferably a resinous room temperaturesetting adhesive having an anaerobic property.

[0150] Where the elastic member 20 in the form of a layer of the bondingmaterial is provided on the engagement surface 18, minute surfaceindentations present on the engagement surface 18 because of its surfaceroughness can be filled up by the bonding material and, accordingly, notonly can a force of engagement of the first annular sealing plate 11onto the inner member 1 be increased, but the gas tightness can also beincreased. The resinous room temperature setting adhesive having ananaerobic property has a low cure rate when in contact with air, but canrelatively quickly cure at room temperatures when applied to theengagement surface 18 where air is barely present. Accordingly, the sizeof a play between the annular sealing plate 11 and the inner member 1for interference fit can be minimized to increase the assemblage.

[0151] Examples of the resinous room temperature setting adhesive havingan anaerobic property that can be employed in the practice of thepresent invention include “Lock-Tight Retaining Compound 680” (productname) and “Lock-Tight 603” (product name) both available from NipponLock-Tight Kabushiki Kaisha.

[0152] Where the elastic member 20 in the form of a thin film is to beprovided at the engagement surface 18 in a manner similar to thatdescribed above, the engagement surface 18 has a surface roughness notgreater than Rmax 3.0, preferably within the range of 0.5 to 2.2.

[0153] Where the annular sealing plate 11 is prepared from a metallicplate, although the surface roughness thereof has hitherto been chosento be within the range of Rmax 3.0 to 7.5, selection of not greater thanRmax 3.0 for the surface roughness is effective to allow the elasticmember 20 to exhibit a sufficient bondability and also to secure theinner diameter to a precise dimension.

[0154] Although in the foregoing embodiment the second annular sealingplate 12 has been shown and described as directly engaged in the outermember 2, an elastic member 24 may also be interposed in an engagement23 between the second annular sealing plate 12 and the outer member 2 asshown in FIG. 6. This elastic member 24 may be in the form of either athin film or a rubber ring.

[0155] Where the elastic member 24 is in the form of a thin film, thesame material as the elastic member 20 at the engagement surface 18 ofthe inner member 1 can be employed and may be in the form of a rubbercoat, a layer of paint or a layer of adhesive material.

[0156] In an embodiment shown in FIG. 7, instead of the use of the thinfilm elastic member 20 as shown in FIG. 1, a portion of the outerperipheral surface of the inner member 1 where the first annular sealingplate 11 is mounted is formed with an annular groove 25 and anring-shaped elastic member 20A made of rubber material is mounted insuch annular groove 25. This ring-shaped elastic member 20A is of a sizehaving its outer periphery protruding a slight distance radiallyoutwardly from the outer diameter of the inner member 1 and, therefore,when the cylindrical wall 11 a of the first annular sealing plate 11 ispress-fitted around the inner member 1, the ring-shaped elastic member20A functions to prevent muddy water from ingressing across theengagement surface 18.

[0157] The ring-shaped elastic member 20A may be employed in the form ofan O-ring and, other than the O-ring, a shaft seal having one or moresealing lips may be employed therefor.

[0158] In an embodiment shown in FIG. 8, instead of the use of the thinfilm elastic member 20 shown in FIG. 1, the structure which will now bedescribed is employed. Specifically, a joint between the cylindricalwall 11 a and the radial wall 11 b of the first annular sealing plate 11is provided with a folded portion 11 c that extends radially inwardlyfrom the radial wall 11 b and joined to the cylindrical wall 11 a afterhaving been turned backwards. This folded portion 11 c is formed duringthe formation of the first annular sealing plate 11 by the use of anyknown press work.

[0159] On the other hand, an outer peripheral edge of the inner member 1is radially inwardly depressed to provide an annular shoulder 26 of anundersized outer diameter. The first annular sealing plate 11 is somounted and so positioned on the outer peripheral surface of the innermember 1 with the cylindrical wall 11 a resting on the inner member 1and with the folded portion 11 c positioned within the annular shoulder26. An ring-shaped elastic member 20B made of rubber material isinterposed between a side wall portion of the annular shoulder 26 andthe folded portion 11 c. The ring-shaped elastic member 20B may be anO-ring or a shaft seal having one or more sealing lips.

[0160] It will readily be seen that when the first annular sealing plate11 having the folded portion 11 c is press-fitted around the innermember 1 with the folded portion 11 c positioned within the annularshoulder 26, a passage for the flow of water becomes tortuous and,therefore, an external water will hardly ingress into the interior ofthe bearing. Also, the intervention of the ring-shaped elastic member20B made of rubber material between the folded portion 11 c and the sidewall of the annular shoulder 26 is effective to secure a fluidtightness. In addition, the provision of the folded portion 11 c in thefirst annular sealing plate 11 is effective to increase the rigidity ofthe first annular sealing plate 11 itself and the press work to form thefirst annular sealing plate 11 can be performed with little elasticregion (spring back) of the material left therein, and any possibledeformation of the first annular sealing plate 11 which would otherwiseoccur when heated to an elevated temperature during a subsequent heattreatment and/or vulcanization of the rubber material for the elasticmember 14 can advantageously be avoided. For this reason, the shapeprecision of the first annular sealing plate 11 can be increased and thesealability due to engagement can further be increased.

[0161] An embodiment shown in FIG. 9 is also similar to the embodimentshown in FIG. 1, but instead of the use of the elastic member 20 in theform of a thin film the structure which will now be described isemployed. An outer peripheral edge of the inner member 11 is radiallyinwardly depressed to provide a generally L-sectioned annular depression27. The cylindrical wall 11 a of the first annular sealing plate 11 ismounted on a portion of the outer peripheral surface of the inner member1 that defines the bottom of the annular depression 27. A ring-shapedelastic member 20C made of rubber material is mounted on that portion ofthe outer peripheral surface of the inner member 1 and interposedbetween an annular radial side face of the depression 27 and an axialfree end 11 aa of the cylindrical wall 11 a of the first annular sealingplate. The ring-shaped elastic member 20C is employed in the form of anO-ring. The annular depression 27 has a radial depth about equal to orsmaller than the thickness of the wall forming the cylindrical wall 11a. The axial free end 11 aa of the cylindrical wall 11 a is chamfered toprovide an annular slant face that is inclined radially downwardlytowards the inner member 1.

[0162] It will readily be seen that when the annular elastic member 20Cmade of rubber material is elastically urged towards the annular radialside face of the depression 27, external water and/or dusts even wheningressing across the engagement surface 18 can be prevented by thering-shaped elastic member 20C from further ingressing into 11 aa theinterior of the bearing. The provision of the annular slant face at theaxial free end of the cylindrical wall 11 a of the first annular sealingplate 11 is effective not only to facilitate insertion of the firstannular sealing plate 11, but also to allow the ring-shaped elasticmember 20 c to deform elastically in a direction radially inwardlythereof, thereby minimizing any possible separation thereof whileserving as a packing. Also, since a major portion of the cylindricalwall 11 a of the first annular sealing plate 11 is held in directcontact with the inner member 1, prevention of any possible separationand/or axial displacement of the first annular sealing plate 11 can bemaximized.

[0163] An embodiment shown in FIGS. 10 and 11 is similar to theembodiment shown in FIG. 1, but differs therefrom in that the followingstructure is added to the sealing device employed in the embodiment ofFIG. 1. Specifically, an axial free end of the cylindrical wall 11 a ofthe first annular sealing plate 11 is bent to protrude radially inwardlyto provide an annular stop pawl lid which is, when the first annularsealing plate 11 is mounted on the inner member 1, engaged in an annulardepression 28 that is defined in a portion of the outer peripheralsurface of the inner member 1 adjacent the associated raceway 1 a. Theradially inwardly extending annular stop pawl 11 d is defined by aradial bent of the axial free end of the cylindrical wall 11 a whereasthe annular depression 28 has a bottom face continued at one end to theraceway 1 a.

[0164] By allowing the annular stop pawl 11 d to engage in the annulardepression 28, any possible axial displacement of the first annularsealing plate 11 can be avoided. It is, however, to be noted that whenthe first annular sealing plate 11 is to be mounted on the inner member1, the axial free end portion of the cylindrical wall 11 a is radiallyoutwardly deformed against its own resiliency as shown by the phantomline in FIG. 11 and is then mounted on the inner member 1 underinterference fit until the annular stop pawl 11 d is brought to aposition immediately above the annular depression 28, after which thefirst annular sealing plate 11 is allowed to restore to the originalshape by the action of its own resiliency. By so doing, the annular stoppawl 11 d can be brought into engagement in the annular depression 28.

[0165] An embodiment shown in FIGS. 12 and 13 is similar to theembodiment shown in FIG. 1, but differs therefrom in that the followingstructure is added to the sealing device employed in the embodiment ofFIG. 1. Specifically, the cylindrical wall 11 a of the first annularsealing plate 11 is formed with a projecting retainer means lie so as toprotrude radially inwardly of the bearing, which projecting retainermeans 11 e is, when the first annular sealing plate 11 is mounted on theinner member 1, engaged in an annular groove 29 defined in the outerperipheral surface of the inner member 1. The projecting retainer means11 e is comprised of a circular row of a plurality of retainerprojections formed at a generally intermediate portion of thecylindrical wall 11 a of the first annular sealing plate 11 so in afashion spaced a distance from each other in a directioncircumferentially of the cylindrical wall 11 a. The annular groove 29 isof a generally V-shaped section and formed on the outer peripheralsurface of the inner member 1 at a location generally intermediatebetween the raceway 1 a and the adjacent end face of the first member 1.The number of the retainer projections 11 e forming the projectingretainer means 11 e is preferably at least three and is preferablyspaced an equal distance from each other in the circumferentialdirection of the inner member 1. Also, each of the retainer projectionsforming the projecting retainer means 11 e may be of a rounded shape, atriangular shape or of a shape resulting from lancing.

[0166] Even when the first annular sealing plate 11 is mounted on thefirst member 1 with the retainer projections of the projecting retainermeans 11 e engaged in the annular groove 29, any possible axialdisplacement of the first annular sealing plate 11 can advantageously beavoided.

[0167] It is to be noted that instead of the projecting retainer means11 e comprised of the plurality of the retainer projections, theprojecting retainer means may be in the form of an annular stop member11 f in the form of an annular projection formed on at a generallyintermediate portion of the cylindrical wall 11 a of the first annularsealing plate 11 so as to extend in a direction circumferentially of thecylindrical wall 11 a as shown in FIG. 14, so that when the firstannular sealing plate 11 is mounted on the inner member 1, the annularstop member 11 f can engage in the annular groove 29 defined in theouter peripheral surface of the first member 1.

[0168] It is also to be noted that where the elements 11 d, 11 e and 11f are employed as is the case with the embodiments shown in FIGS. 10 to14, respectively, the elastic member 20 may be in the form of a thinfilm or a ring-shaped rubber member such as described in connection withthe embodiment shown in FIG. 1.

[0169] Respective embodiments shown in FIGS. 15 to 20 are thoseaccording to the second aspect of the present invention.

[0170] The embodiment shown in FIG. 15 is, except for what will now bedescribed below, similar to the embodiment shown in FIG. 1. According tothe embodiment shown in FIG. 15, instead of the use of the elasticmember 20 employed in the first annular sealing plate 11 shown in FIG.1, the elastic member 14 forming the encoder grid has an elastic tongue30 protruding outwardly therefrom is elastically held in contact with aconnecting member 31 that is held in abutment with the annular end faceof the inner member 1. The elastic tongue 30 is of a shape in a naturalstate as shown by the chain line therein when it is not elasticallydeformed.

[0171] The connecting member 31 may be, for example, a constant speeduniversal coupling 7 having an annular shoulder 7 a adapted to be heldin abutment with the annular end face of the inner member 1 as shown inthe example of FIG. 3. As shown therein, the elastic tongue 30 (FIG. 15)integral with the elastic member 14 is held in engagement with an outerperipheral face of the annular shoulder 7 a of the constant speeduniversal coupling 7. Although in the example shown in FIG. 15, theconstant speed universal coupling 7 is shown as engaging a portion ofthe inner peripheral surface of the inner member 1, the constant speeduniversal coupling 7 may be engaged with an inner peripheral surface ofthe barrel hub 6 where as is the case with the example shown in FIG. 3the inner member 1 is constituted by the separate inner race 1A mountedexternally on one end of the barrel hub 6.

[0172] The elastic tongue 30 protruding outwardly from the elasticmember 14 extends slantwise in a direction axially of the bearing froman inner peripheral edge of the elastic member 14 over the entirecircumference thereof and has a thickness smaller than the body of theelastic member 14 forming the encoder grid. The elastic tongue 30 may bemade of the same material as that for the elastic member 14 and, wherethe same material as that for the elastic member 14 is employed for theelastic tongue 30, bonding by vulcanization to the first annular sealingplate 11 can be performed simultaneously with that of the elastic member14 to the radial wall 11 b of the first annular sealing plate 11,resulting in an advantage in terms of cost.

[0173] Although the elastic member 14 is shown to be of a configurationhaving an overhang portion 14 a covering a radial outer circumferentialportion of the radial wall 11 b of the first annular sealing plate 11 ina generally capped fashion from an outer surface to an inner surface ofthe free end thereof, this overhang portion 14 a may be dispensed withif so desired.

[0174] The elastic member 16 integrated together with the second annularsealing plate 12 is shown to be of a configuration having an overhangportion 16 d covering an axial free end of the cylindrical wall 12 a ofthe second annular sealing plate 12 in a generally capped fashion froman inner surface to an outer surface thereof, this overhang portion 16may be dispensed with if so desired.

[0175] In the example shown in FIG. 15, the overhang portion 14 a of theelastic member 14 provided on the first annular sealing plate 11 and theoverhang portion 16 d of the elastic member 16 provided on the secondannular sealing plate 12 cooperate to define a radial gap which forms alabyrinth seal 17.

[0176] It is to be noted that although in the example shown in FIG. 15,the radial wall 12 b of the second annular sealing plate 12 is shown asconfigured to represent a generally S-shape, the radial wall 12 b may beflat as is the case with that in the example shown in FIG. 1.

[0177] In the embodiment shown in FIG. 15, since the elastic tongue 30protruding from the elastic member 14 is elastically held in contactwith the outer peripheral surface of the connecting member 31, anypossible ingress of water and/or dusts into the interior of the bearingcan advantageously be avoided. Also, since the first annular sealingplate 11 is directly engaged with the inner member 1, a sufficient forceof engagement can be secured.

[0178] It is to be noted that the example of FIG. 15 is such that theannular shoulder of the connecting member 31 with which the inner member1 is connected is of a relatively great diameter. Where the diameter ofthe annular shoulder of the connecting member 31 is relatively small,the tongue 30 should have a relatively great length as shown in FIG. 16.

[0179] In an embodiment shown in FIG. 17, the outer peripheral edge ofthe inner member 1 is radially inwardly depressed to provide a generallyL-sectioned annular depression 32 for accommodating the elastic tongue30 that protrudes from the elastic member 14 so as to elastically engagean annular side face of the connecting member 31. The elastic tongue 30has an annular lateral protuberance 30 a at an inner peripheral portionthereof, said annular lateral protuberance 30 a protruding towards theannular side face of the connecting member 31 for engagement with anannular side face of the shoulder of the connecting member 31.

[0180] With the structure shown in FIG. 17, since the annular lateralprotuberance 30 is brought into engagement with the annular side face ofthe connecting member 31, the sealing device 5 including the elastictongue 30 can be standardized without being adversely affected by thedimension of the outer peripheral surface of the shoulder of theconnecting member 31.

[0181] Other structural features of the sealing device 5 employed in theembodiment shown in FIG. 17 are substantially similar to those employedin the embodiment shown in FIG. 15.

[0182] In an embodiment shown in FIG. 18, the outer peripheral edge ofthe inner member 1 is radially inwardly depressed to provide a generallyL-sectioned annular depression 33 for accommodating the cylindrical wall11 a of the first annular sealing plate 11. Specifically, the firstannular sealing plate 11 is mounted on the first member 1 with thecylindrical wall 11 a thereof press-fitted to a bottom face of theannular depression 33 which is a part of the outer peripheral surface ofthe inner member 1 that is radially inwardly depressed. The cylindricalwall 11 a of the first annular sealing plate 11 employed in thisembodiment of FIG. 18 is relatively short having a length somewhatgreater than the wall thickness thereof The radial wall 11 b of thefirst annular sealing plate 11 is then held partially in contact with anannular side face of the annular depression 33. The elastic radialsealing lips 16 b and 16 c carried by the second annular sealing plate12 are held in sliding contact with the outer peripheral surface of theinner member 1. The elastic tongue 30 protruding from the elastic member14 forming the encoder grid is elastically engaged with an annular sideface of the shoulder of the connecting member 31 within the annulardepression 33. In such case, the elastic tongue 30 has a thickness in anatural state which is greater than the size of a gap between the radialwall 11 b and the annular side face of the shoulder of the connectingmember 31 as shown by the phantom line in FIG. 18, but is, in anassembled condition, compressed inwardly in contact with the annularside face of the connecting member 31.

[0183] With the structure shown in FIG. 18, since the elastic radialsealing lips 16 b and 16 c carried by the second annular sealing plate12 are held in direct contact with the inner member, the sealability canbe increased. Also, since the elastic tongue 30 is held in contact withand is therefore inwardly compressed in contact with the annular sideface of the shoulder of the connecting member 31, the sealability canfurther be increased.

[0184] Where the annular depression 33 for accommodating the cylindricalwall 11 a of the first annular sealing plate 11 is employed in the firstmember 1, the first annular sealing plate 11 may be prepared from, andbe of a configuration representing, an annular plate having an innerbore through which the first annular sealing plate 11 can bepress-fitted. However, the annular plate as formed by a blankingtechnique would not provide a sufficient accuracy and a sufficientbinding force and, therefore, difficulty will arise in alignment of theencoder grid with the elastic member 14 in view of the squareness of theradial wall 11 b. However, the use of the cylindrical wall 11 a of arelatively small axial length is effective to secure the binding forceand to accomplish the highly accurate alignment.

[0185] Other structural features of the sealing device 5 employed in theembodiment shown in FIG. 18 are substantially similar to those employedin the embodiment shown in FIG. 15.

[0186] According to an embodiment shown in FIG. 19, the elastic tongue30 protruding from the elastic member 14 is elastically engaged with aconnecting member 35 then held in abutment with an annular end face ofthe inner member 1. In this embodiment, the connecting member 35 isdefined by a crimped portion of the barrel hub 6 which is crimpledradially outwardly to confront the axial end of the separate inner race1A then held in abutment with one end of the barrel hub 6. The separateinner race 1A serves as the inner member 1, and the barrel hub 6 and theseparate inner race 1A are formed, for example, in a manner similar tothose shown in the example of FIG. 3. In the example shown in FIG. 3, acrimp projection of a cylindrical configuration extending axially fromthe barrel hub 6 is formed and is, after the separate inner race 1A hasbeen engaged, crimped radially outwardly in the form of a radial flangeto retain the separate inner race 1A in position. The crimped portionrepresenting the shape of a radial flange so formed constitute theconnecting member 35. The elastic tongue 30 is adapted to be elasticallyheld in contact with an outer peripheral surface of the connectingmember 35 defined by the crimpled portion.

[0187] In the structure according to the embodiment shown in FIG. 19, bythe utilization of the connecting member 35 defined by the crimpedportion, the sealability can be secured owing to the elastic contact ofthe elastic tongue 30 with no need to increase the size of the elastictongue 30.

[0188] Other structural features of the sealing device 5 employed in theembodiment shown in FIG. 19 are substantially similar to those employedin the embodiment shown in FIG. 15.

[0189] Instead of the elastic tongue 30 which is, in the embodimentshown in FIG. 19, engaged with the outer peripheral surface of theconnecting member 35, the crimped portion of the connecting member 35may be formed with a radially inwardly extending annular step 36 so thatthe elastic tongue 30 can be elastically engaged with an annular sideface of the annular step 36 as shown in FIG. 20.

[0190] Respective embodiments shown in FIGS. 21A and 21B and FIG. 22pertains to those according to the third aspect of the presentinvention.

[0191] The embodiment shown in FIGS. 21A and 21B is, except for whatwill now be described below, similar to the embodiment shown in FIG. 1.According to the embodiment shown in FIGS. 21A and 21B, of the first andsecond annular sealing plates 11 and 12, at least the first annularsealing plate 11 is formed with a metallic layer 37 on a surface of asteel plate made of a magnetic material. The metallic layer 37 is madeof a metal having a Young's modulus of elasticity which is lower thanthat of the inner member 1. In the example shown therein, both of thefirst and second annular sealing plates 11 and 12 are formed with therespective metallic layers 37. The metallic layer 37 is, for example, ametal plating. The inner member 1 is made of, for example, steelmaterial such as bearing steel. The metal having the lower Young'smodulus of elasticity may be chosen from the group consisting of zinc,tin, gold, silver and copper. The metallic layer 37 has a thicknesswithin the range of 5 to 30 μm. In particular, where the metallic layer37 is a metal plating, the thickness of the metallic layer 37 ispreferred to be within this range.

[0192] Since the first annular sealing plate 11 is formed with themetallic layer 37, a magnetic material having a high physical strength,for example, a rolled steel plate (a cold rolled steel plate such asSPCC) or carbon tool steel such as, for example, SK5, or carbon steelplate such as, for example, S45C can be employed as a material for thefirst annular sealing plate 11, with no need to use an expensivestainless steel. Even though such a steep plate is employed as amaterial for the first annular sealing plate 11, a relatively high rustproof can be obtained since the first annular sealing plate 11 iscovered by the metallic layer 37 having a rust proof property. The useof such an inexpensive steel plate is advantageous in terms of cost.Also, where the second annular sealing plate 12 is covered by themetallic layer 37, the rust proof can be increased and there is no needto select material highly resistant to rusting and an inexpensivematerial can be selected. It is, however, to be noted that the secondannular sealing plate 12 is preferably prepared from a non-magneticmetal plate.

[0193] An engagement surface 1 b of the inner member 1 on which thefirst annular sealing plate 11 is mounted is machined simultaneouslywith machining of the raceway 1 a to thereby form a plunge cut surface.The engagement surface 1 b has a surface roughness not greater than Rmax3.0 or not greater than Ra 0.63 and is preferably within the range ofRmax 0.5 to 2.2. The surface roughness of a steel plate an engagementsurface 11 ab of the first annular sealing plate 11 that is held incontact with the inner member 1 is not greater than Rmax 3.0 or notgreater than Ra 0.63 and is preferably within the range of Rmax 0.5 to2.2.

[0194] Because of the surface roughness and the shape precision of theengagement surface 1 b of the inner member 1, minute surfaceirregularities are formed at an engagement portion between the firstannular sealing plate 11 and the inner member 1, and also similar minutesurface irregularities are formed in the steel plate at the engagementsurface 11 ab of the first annular sealing plate 11. However, since themetallic layer 37 having the Young's modulus of elasticity lower thanthat of the inner member 1 is formed on the surface of the first annularsealing plate 11, detents of the minute surface irregularities arefilled up by soft metal forming the metallic layer 37, resulting inincrease of the sealability. Accordingly, any possible degradation ofthe grease which would otherwise result from ingress of water into theinterior of the bearing can be prevented, resulting in increase of thelifetime of the bearing. Since the first annular sealing plate 11 makesuse of the steel plate, the magnetic flux density of the encoder gridcan be increased. Also, since the metallic layer on the surface of thesteel plate is relatively thin, it will little affect the magnetic fluxdensity.

[0195] In addition, since the first annular sealing plate is providedwith the metallic layer 37, the first annular sealing plate 11 even whenprepared from any of the various steel plates such as, for example, arolled steel plate which is a magnetic material having a high physicalstrength, a sufficient rust proof can be obtained. For this reason, withno need to use an expensive stainless steel or the like, an advantage interms of cost can be appreciated.

[0196] Where the thickness of the metallic layer 37 is chosen to bewithin the range of 5 to 30 μm, the minute surface irregularitiesresulting from the surface roughness of the engagement surface can befilled sufficiently and the flatness of the engagement surface can alsobe secured, resulting in reduction in cost. In other words, if thesurface roughness of the engagement surface 1 b of the inner member 1 onwhich the first annular sealing plate 11 is mounted is about Rmax 3.0(or Ra 0.63), and in order for the resultant minute surfaceirregularities to be filled up, the thickness of the metallic layer hasto be at least not smaller than 5 μm. On the other hand, even if thisthickness is chosen to be not smaller than 30 μm, effects brought aboutthereby remain the same and, conversely, the evenness (or flatness) willbe adversely affected, requiring an increased length of time to form themetallic layer 37 together with increase of the cost. For this reason,the thickness of the metallic layer 37 is preferred to be within theabove mentioned range.

[0197] If the surface roughness of the engagement surface 11 ab of thefirst annular sealing plate 11 is chosen to be not greater than Rmax3.0, particularly within the range of Rmax 0.5 to 2.2, the effect of themetallic layer 37 to fill up the minute surface irregularities resultingfrom the surface roughness can be increased.

[0198] If the engagement surface 1 b of the inner member 1 is machinedto define the plunge cut surface, the raceway la and the engagementsurface 1 b can be simultaneously formed by machining and any possiblemisalignment therebetween can be prevented. In the case of the plungecut surface, machining to form the engagement surface 1 b having thesurface roughness not greater than Rmax 3.0 can easily be performed and,by increasing of the surface evenness in this way, the sealability canfurther be increased.

[0199] It is to be noted that in the foregoing embodiments the use hasbeen made of the elastic side sealing lip 16 a and the two elasticradial sealing lips 16 c and 16 b positioned on respective sides of theassociated radial wall 12 b with respect to the axial direction of thebearing as shown in FIG. 21. However, the axially outer elastic radialsealing lip 16 b may be replaced with an elastic side sealing lip asshown in FIG. 22 or may be dispensed with if so desired.

[0200] Respective embodiments shown in FIGS. 23 to 29 pertains to thoseaccording to the fourth aspect of the present invention.

[0201] The embodiment shown in FIG. 23 is, except for what will now bedescribed below, similar to the embodiment shown in FIG. 1. According tothe embodiment shown in FIG. 23, the first annular sealing plate 11 hasits cylindrical wall 11 a engaged with an outer peripheral surface of aradially inwardly extending annular depression 38 formed on the outerperipheral surface of the inner member 1. The annular depression 38 hasa depth corresponding to the thickness of the first annular sealingplate 11 and defines a reduced outer diameter portion of the innermember 1. This annular depression 38 has an axial length so chosen as toallow the axial free end of the cylindrical wall 11 a of the firstannular sealing plate to engage an annular side wall of the annulardepression 38. By way of example, the axial length of the annulardepression 38 is about equal to the axial length of the cylindrical wall11 a.

[0202] The second annular sealing plate 12 is integrated together withthe elastic side sealing lip 16 a, slidingly engageable with the radialwall 11 b of the first annular sealing plate 11, and the elastic radialsealing lip 16 b slidingly engageable with an outer peripheral surface19 of the inner member 1 adjacent the engagement surface 18, or thecylindrical wall 11 a, of the first annular sealing plate 11. Theseelastic sealing lips 16 a and 16 b form respective parts of the elasticmember 16 made of an elastomer and bonded by vulcanization to the secondannular sealing plate 12. The elastic side sealing lip 16 a has its freeend portion inclined so as to extend towards a radial inner edge of theradial wall 11 b of the first annular sealing plate 11 whereas theelastic radial sealing lip 16 b has its free end portion inclined so asto extend towards the interior of the bearing.

[0203] The radial wall 12 b of the second annular sealing plate 12 isbent to represent a generally S-shaped or Z-shaped configuration so thata base portion thereof adjacent the joint between the cylindrical wall12 a and the radial wall 12 b can protrude towards the interior of thebearing beyond the free end portion of the radial wall 12 b. Thisconfiguration permits the second annular sealing plate 12 to have anincreased rigidity and also permits the elastic member 16 to be formedto have an increased wall thickness.

[0204] According to the wheel bearing of the structure shown in anddescribed with reference to FIG. 23, the seal between the inner andouter members 1 and 2 can be created by the sliding engagement of theelastic sealing lips 16 a and 16 b provided in the second annularsealing plate 12 and the labyrinth seal 17 at the annular gap betweenthe cylindrical wall 12 a of the second annular sealing plate 12 and theouter peripheral edge of the radial wall 11 b of the first annularsealing plate 11. The elastic radial sealing lip 16 b is slidinglyengaged with the outer peripheral surface adjacent the annular sealingplate engagement of the inner member 1 which is the rotary member and,therefore, even when water ingresses across the engagement 18 betweenthe first annular sealing plate 11 and the inner member 1, furtheringress of the water into the interior of the bearing can be preventedby the sliding engagement of the elastic radial sealing lip 16 b. Forthis reason, there is no possibility of the grease being deteriorated incontact with water and the lifetime of the bearing can therefore beincreased. Also, since the sealability can be secured by the elasticradial sealing lip 16 b, the material for the first annular sealingplate 11 may not be limited and the use of a suitable ferromagneticmaterial makes it possible to increase the magnetic flux density of theencoder grid defined by the elastic member 14 provided on the radialwall 11 b of the first annular sealing plate 11.

[0205] Also, since the inner member 1 is provided with the annulardepression 38 and the first annular sealing plate 11 is mounted in theannular depression 38, any possible axial displacement of the firstannular sealing plate towards the interior of the bearing can beavoided, the position where the first annular sealing plate 11 isarranged with respect to the axial direction is regulated and a properplay for the elastic side sealing lip 16 a can be retained. Since theabove described annular depression 38 has a depth corresponding to thewall thickness of the cylindrical wall 11 a of the first annular sealingplate 11, there is neither a problem associated with any possiblereduction in strength of the inner member 1 resulting from the formationof the annular depression 38 and a problem associated with the increasein size of the first annular sealing plate 11, and any possibleinsufficient engagement due to the relatively small depth of the annulardepression 38 can also be avoided.

[0206] Another embodiment according to the fourth aspect of the presentinvention is shown in FIG. 24. This embodiment of FIG. 24 issubstantially similar to that shown in FIG. 23, except that the elasticradial sealing lip 16 b which has been described as having its free endportion inclined so as to extend towards the interior of the bearing inthe previously described embodiment of FIG. 23 has its free end portioninclined in a direction axially outwardly of the bearing. Otherstructural features of the sealing device 5 employed in the embodimentshown in FIG. 24 are substantially similar to those employed in theembodiment shown in FIG. 23.

[0207] According to the embodiment shown in FIG. 24, if the free endportion of the elastic radial sealing lip 16 b is inclined so as textend axially outwardly of the bearing, the effect of preventing waterfrom ingressing from the outside of the bearing into the interior of thebearing can be increased advantageously. For this reason, wateringressing across the engagement 18 and the elastic side sealing lip 16a from the outside of the bearing can be assuredly prevented fromfurther ingressing into the interior of the bearing past the elasticradial sealing lip 16 b.

[0208]FIG. 25 illustrates a further embodiment according to the fourthaspect of the present invention. The embodiment of FIG. 25 issubstantially similar to that shown in FIG. 24, except that in theembodiment of FIG. 25 the elastic side sealing lip 16 a is formed at twolocation spaced a distance radially inwardly and outwardly. Otherstructural features of the sealing device 5 employed in the embodimentshown in FIG. 25 are substantially similar to those employed in theembodiment shown in FIG. 24.

[0209] The elastic side sealing lip 16 a is effective to exhibit aprimary function of preventing water from ingressing from the outside ofthe bearing into the interior of the bearing and, therefore, theprovision of such elastic side sealing lip 16 a at the radially innerand outer locations as described above, the function of preventing waterfrom ingressing into the interior of the bearing can be enhanced.

[0210]FIG. 26 illustrates a still her embodiment according to the fourthaspect of the present invention. In this embodiment, an outer peripheralface of the overhang portion 14 a in the first annular sealing plate 11is formed with a radially outwardly protruding annular protrusion 14 aaon one side adjacent the interior of the bearing and, on the other hand,an inner peripheral face of the overhang portion 16 d in the secondannular sealing plate 12 is also formed with a radially inwardlyprotruding annular protrusion 16 da. The radially outwardly and inwardlyprotruding annular protrusions 14 aa and 16 da define the maximumdiameter portion at the free end of the radial wall 11 b of the firstannular sealing plate 11 and a minimum diameter portion at the axial endof the cylindrical wall 12 a of the second annular sealing plate 12,respectively The radially outwardly protruding annular projection 14 aais positioned inwardly of the bearing with respect to the radiallyinwardly protruding annular projection 16 da and has its diameter ofouter periphery greater than that of the inner periphery of the radiallyinwardly protruding annular projection 16 da. Respective faces of theradially outwardly and inwardly protruding annular projections 14 aa and16 da are formed as inclined faces substantial parallel to each other.Other structural features of the sealing device 5 employed in theembodiment shown in FIG. 26 are substantially similar to those employedin the embodiment shown in FIG. 25.

[0211] In the case of this structure, when the radially outwardly andinwardly protruding annular projections 14 aa and 16 da are engaged witheach other in the axial direction, any possible separation between thefirst and second annular sealing plates 11 and 12 can be avoided duringan assemblage thereof into the bearing. In other words, since with thebasic structure the annular radial sealing lip 16 b in the secondannular sealing plate 12 is not in sliding contact with the outerperipheral surface 19 of the inner member 1, they are in a conditionhaving not yet been assembled into the bearing and the first and secondannular sealing plates 11 and 12 will be separated relative to eachother. For this reason, transportation and an assemblage into thebearing are complicated, accompanied by increase in number ofmanufacturing steps. In contrast thereto, allowing the radiallyoutwardly and inwardly protruding annular projections 14 aa and 16 da tobe engaged with each other in the axial direction is effective toeliminate the possible separation between the first and second annularsealing plates 11 and 12 in a condition having not yet been assembledand they can be dealt with as a single component part. Accordingly, notonly at the time of transportation, but the number of assembling stepsinto the bearing can be reduced, thereby facilitating the assemblage.Also, the provision of the radially outwardly and inwardly protrudingannular projections 14 aa and 16 da allows the gap forming the labyrinthseal 17 to represent a generally tortuous shape, resulting in increaseof the sealability. Also, since the radially outwardly and inwardlyprotruding annular projections 14 aa and 16 da are formed by utilizingrespective portion of the associated elastic members 14 and 16, thefirst and second annular sealing plates can be forcibly separated orassembled by forcibly moving the first and second annular sealing plates11 and 12 in the axial direction to deform the projections 14 aa and 16da.

[0212] It is to be noted that in the embodiment shown in FIG. 26 thefirst and second annular sealing plates 11 and 12 have been shown asincluding the respective overhang portions 14 a and 16 d, with theradially outwardly and inwardly protruding annular projections 14 aa and16 da formed thereon, respectively. However, one of the overhangportions 14 a and 16 d may be dispensed with if so desired.

[0213] By way of example, as shown in FIG. 27, an axial end 12 aa of thecylindrical wall 12 a of the second annular sealing plate 12 may beexposed to the outside and is so bent as to occupy a position radiallyinwardly of the bearing, and the radially outwardly protruding annularprojection 14 aa engageable therewith in the axial direction may beformed on the overhang portion 14 a in the first annular sealing plate11. In the case of this arrangement, any possible separation of thefirst and second annular sealing plates 11 and 12 in a condition havingnot yet been assembled can be prevented.

[0214] Conversely, the radially outer edge of the radial wall 11 b ofthe first annular sealing plate 11 may be exposed, and the overhangportion 16 d on the cylindrical wall 12 a of the second annular sealingplate 12 may be formed with the radially inwardly protruding annularprojection 16 da (FIG. 26) engageable with an radially outer edge of theradial wall 11 b of the first annular sealing plate 11 then exposed.

[0215]FIG. 28 illustrates a still further embodiment according to thefourth aspect of the present invention. The embodiment shown in FIG. 28is substantially similar to that shown in FIG. 23, except that in theembodiment of FIG. 28, in place of the elastic radial sealing lip 16 bprotruding outwardly from the elastic member 16 shown in FIG. 23, twoelastic radial sealing lips 16 b 1 and 16 b 2 are employed. The elasticradial sealing lip 16 b 1 has its free end portion extending slantwisein a direction inwardly of the bearing while the elastic radial sealinglip 16 b 2 has its free end portion extending slantwise in a directionoutwardly of the bearing.

[0216] The use of the elastic radial sealing lip 16 b 2 extendingslantwise in a direction outwardly of the bearing enhances an effect ofpreventing water from ingressing from the outside of the bearing intothe interior of the bearing. The elastic radial sealing lip 16 b 1having its free end portion extending slantwise in a direction inwardlyof the bearing functions to prevent the grease from leaking to theoutside of the bearing. Other structural features of the sealing device5 employed in the embodiment shown in FIG. 28 are substantially similarto those employed in the embodiment shown in FIG. 23.

[0217] A yet further embodiment according to the fourth aspect of thepresent invention is shown in FIG. 29. The embodiment of FIG. 29 issubstantially similar to that shown in FIG. 28, except that in theembodiment of FIG. 29, the outer peripheral surface 1 b of the innermember 1 delimited between the raceway 1 a and the annular end face ofthe inner member 1 is made flat. In other words, the annular depression38 employed in the inner member 1 shown in FIG. 28 is eliminated. Theinner member 1 is comprised of an inner race. Other structural featuresof the sealing device 5 employed in the embodiment shown in FIG. 29 aresubstantially similar to those employed in the embodiment shown in FIG.28.

[0218] Where the outer peripheral surface 1 b of the inner member 1 ismade flat and without any annular depression, the entire section of thesealing device 5 may be smaller than that shown in FIG. 28, but arelatively large sliding space can be available for the elastic radialsealing lip 16 b 1 which serves as a grease sealing lip and whichextends slantwise in a direction inwardly of the bearing. For thisreason, the space defined in the bearing in an axial direction thereofcan be reduced, resulting in a large freedom of design choice. For agiven space in the axial direction, the bearing span can be increased,resulting in increase of the rigidity.

[0219] It is to be noted that in any one of the embodiments shownrespectively in FIGS. 23 to 27, the outer peripheral surface of theinner member 1 delimited between the raceway 1 a and the annular endface of the inner member 1 may be made flat as is the case with thatshown in FIG. 29. In other words, the outer peripheral surface 19 in itsentirety may be a cylindrical surface of the same diameter with noannular depression 38 employed.

[0220] In any one of the foregoing embodiments except for that shown inFIG. 29, (that is, in any one of the foregoing embodiments in which theannular depression 38 is formed in the outer peripheral surface of theinner member 1), various portion of the inner member 1 which eventuallyserves as the inner race are simultaneously ground by the use of anintegrated grinding stone 40 as shown in FIG. 30. In other words, areduced diameter end face 1 c, a counter-bore portion 1 d, a raceway la,an outer peripheral surface 19 and an annular depression 38, all foundin the inner member 1, are simultaneously ground by the use of theintegrated grinding stone 40. The grinding stone 40 is urged slantwisetowards the inner member 1 as shown by the arrow in FIG. 30 to performan angular cutting. The reason for the simultaneous grinding of thevarious parts of the inner member 1 is for the purpose of increasing theconcentricity of the various parts of the inner member 1 and also forthe purpose of precisely machining to exactly attain a pitch P1 betweenthe reduced diameter end face 1 c and the raceway 1 a. This pitch P1 isassociated with the bearing gap.

[0221] Embodiments shown respectively in FIGS. 31 to 36 pertains tothose according to the fifth aspect of the present invention. In theseembodiments, component parts similar to those shown in connection withthe previously described embodiments are shown by like referencenumerals.

[0222] In the embodiment shown in FIG. 31, the sealing device 5 is shownas applied to the rolling bearing of a type in which the inner race 1 isrotatable. The sealing device 5 shown therein includes the slinger (thefirst annular sealing plate) 11 being a metallic member on the side ofthe inner race 1 and mounted on an outer peripheral surface of an axialend of the inner race 1, a core metal (the second annular sealing plate)12 being a metal member on the side of the outer race 2 and mounted onan inner peripheral surface of an axial end of the outer race of thebearing, a sealing member 16 mounted on the core metal 12 and slidinglyengaged with the slinger 11, an annular rubber magnet 14 bonded byvulcanization coaxially to an outer side face of the slinger 11 andhaving a magnetized portion, and an elastic member 20 interposed betweenthe slinger 11 and the inner member 1 and made of a material dissimilarto that of the rubber magnet (elastic member) 14.

[0223] The slinger 11 is formed with a cylindrical wall 11 a and aflange (the radial wall) 11 b radially outwardly extending from anaxially inner end of the cylindrical wall 11 a in a direction towardsthe outer race 2, and the core metal 12 is formed with a cylindricalwall 12 a press-fitted on an inner peripheral surface of thecorresponding axial end of the outer race 2 and a flange (the radialwall) 12 b radially inwardly extending from an axially inner end of thecylindrical wall 12 a adjacent the row of the rolling element 3 in adirection towards the inner race 1. The axially outer end 12 aa of thecylindrical wall 12 a of the core metal 12 is somewhat inwardly bent toaccommodate the sealing member 16.

[0224] The sealing member 16 includes two elastic radial sealing lips 16b and 16 c slidingly engageable with an inner peripheral surface of thecylindrical wall 11 a of the slinger 11 and an elastic axial sealing lip16 a slidingly engageable with an annular inner surface of the slinger11, and an angled annular projection 16 e is integrally formed with afree end of a generally L-shaped bent portion 16 f on one side oppositeto the elastic axial sealing lip 16 a. The sealing member 16 is mountedon the axially outer end 12 aa of the cylindrical wall 12 a and theflange 12 b of the core metal 12 with the annular projection 16 epositioned on an outer peripheral surface of the flange 12 b. Asschematically shown in FIG. 36A, the annular projection 16 e is soformed as to be of a ring-shape extending circumferentially and as toprotrude axially inwardly towards the row of the rolling elements 3. Inother words, the embodiment of FIG. 31 is substantially similar to theembodiment according to the first aspect of the present invention shownin FIG. 1, except for the annular projection 16 e added in accordancewith the embodiment shown in FIG. 31.

[0225] Although the annular projection 16 e has been formed in aring-shape integrally with the sealing member 16, it may be possiblethat in place of the annular projection 16 e, a plurality of separateprojections 16 g extending discontinuously in the circumferentialdirection may be formed as schematically shown in FIG. 36B, in whichcase the minimum required number of those separate projections 16 g maybe three.

[0226] The annular rubber magnet 14 bonded by vulcanization coaxially tothe outer peripheral side of the flange 11 b of the slinger 11 isprepared by mixing rubber material with a powder of magnetic particlesof, for example, barium (Ba) ferrite, vulcanizing and molding themixture, and magnetizing N and S poles alternating in thecircumferential direction.

[0227] In order to increase the strength of the magnetic field developedby the rubber magnet 14 to facilitate a speed detection during a speedcontrol, the slinger 11 which is the metallic member mounted on therotary side is preferably made of a magnetic material. Examples of thismagnetic material are many, but ferrite stainless steels are preferredbecause they have a corrosion resistance effective to suppress rusting.Of those ferrite stainless steel materials, SUS 430 now on massproduction is more preferred because of an excellent workability.

[0228] When the sealing device 5 is to be press-fitted to the bearing,as shown in FIG. 35, a plurality of the sealing devices 5 of anidentical structure are placed on a support table 41 with the core metal12 oriented downwards while the slinger 11 bonded by vulcanization withthe rubber magnet 14 is oriented upwards. In such case, since the outerside face of the flange 12 b of the core metal 12 of each of the sealingdevices 5 is provided with the annular projection 16 e formed integrallywith the sealing member 16 in a continuous ring form, the rubber magnet14 in one of the sealing devices 5 and the core metal 12 in the other ofthe sealing devices 5 stacked immediately above such one of the sealingdevices 5 will not contact with each other when the sealing devices 5are stacked one above the other on the support table 41, except for atip of the annular projection 16 e in such other of the sealing devices5. Accordingly, in the stacked condition, a space S corresponding to theamount of protrusion of the annular projection 16 e from the outer sideface of the flange 12 b of the core metal 12 can be obtained between theneighboring sealing devices 5.

[0229] The presence of the space S serves to weaken the magnetic forceof attraction exerted by the rubber magnet 14 to attract the core metal12 and does therefore prevents the neighboring sealing devices 5 frombeing magnetically attracted to each other, thereby allowing the sealingdevices 5 to be transported one by one into a chute by a handling deviceof an automatic press-fitting machine with no trouble to therebyaccomplish an automatic press-fitting of each of the sealing devicesinto the corresponding bearing one at a time.

[0230] In the embodiment shown in FIG. 32, the sealing device 5 is shownas applied to the rolling bearing of a type in which the outer race 2 isrotatable. The sealing device 5 shown therein includes the slinger (thefirst annular sealing plate) 11 being a metallic member on the side ofthe outer race 2 and mounted on an inner peripheral surface of an axialend of the outer race 2, a core metal (the second annular sealing plate)12 being a metal member on the side of the inner race 1 and mounted onan outer peripheral surface of an axial end of the inner race 1, asealing member 16 mounted on the core metal 12 and slidingly engagedwith the slinger 11, an annular rubber magnet 14 bonded by vulcanizationcoaxially to an outer side face of the flange 11 b of the slinger 11 andhaving a magnetized portion, and an elastic member 20 interposed betweenthe slinger 11 and the outer race 2. The angled annular projection 16eis formed integrally with the sealing member 16 as is the case with thepreviously described embodiment and is positioned on an outer side ofthe flange 12 b of the core metal 12 while extending continuously in acircumferential direction (See FIG. 36A) so as to protrude inwardly ofthe bearing, that is, in a direction towards the row of the rollingelements 3. In place of the annular projection 16 e, as is the case withthe embodiment shown in FIG. 31 (See FIG. 36B), circumferentiallydiscontinuous projections 16 g may be formed, in which case the minimumrequired number of those discontinuous projections 16 g is three.

[0231] Even in this embodiment shown in FIG. 32, as is the case with theembodiment shown in FIG. 35, the stack of the sealing devices 5 placedon the support table 41 with the core metal 12 in one of the sealingdevices 5 positioned below the slinger 11 in the other of the sealingdevices 5 which is bonded by vulcanization with the rubber magnet 14 arespaced from each other a distance corresponding to the space S which inturn corresponds to the amount of protrusion of the annular projection16 e. The presence of the space S between the neighboring sealingdevices 5 prevents the neighboring sealing devices 5 from beingmagnetically attracted to each other, thereby allowing the sealingdevices 5 to be automatically press-fitted into the correspondingbearing one at a time smoothly.

[0232] In the embodiment shown in FIG. 33, the sealing device 5 is shownas applied to the rolling bearing of a type in which the inner race 1 isrotatable, as is the case with the embodiment shown in FIG. 31. Thesealing device 5 shown therein includes the slinger 11 mounted on anouter peripheral surface of an axial end of the inner race 1, a coremetal 12 mounted on an outer peripheral surface of an axial end of theouter race 2, and a sealing member 16 mounted on the core metal 12 andslidingly engaged with the slinger 11. An outer side face of the flange11 b of the slinger 11 made of a magnetic material has a magnetizedportion 14A in which opposite magnetic poles are magnetized alternatelyin a circumferential direction thereof The annular projection 16e isformed integrally with the sealing member 16 as is the case with thepreviously described embodiments and is positioned on the outer sidesurface of the flange 12 b of the core metal 12. This annular projection16 e extends continuously in a circumferential direction thereof in aring form (See FIG. 36A) so as to protrude inwardly of the bearing, thatis, in a direction towards the row of the rolling elements 3.

[0233] In the embodiment shown in FIG. 34, the sealing device 5 is shownas applied to the rolling bearing of a type in which the outer race 2 isrotatable. The sealing device 5 shown therein includes the slinger 11mounted on an inner peripheral surface of an axial end of the outer race2, a core metal 12 being a metal member on the side of the inner race 1and mounted on an outer peripheral surface of an axial end of the innerrace 1, and a sealing member 16 mounted on the core metal 12 andslidingly engaged with the slinger 11. An outer side face of the flange11 b of the slinger 11 made of a magnetic material has a magnetizedportion 14A in which opposite magnetic poles are magnetized alternatelyin a circumferential direction thereof. The annular projection 16 e isformed integrally with the sealing member 16 as is the case with thepreviously described embodiments and is positioned on the outer sidesurface of the flange 12 b of the core metal 12. This annular projection16 e extends continuously in a circumferential direction thereof in aring form (See FIG. 36A) so as to protrude inwardly of the bearing, thatis, in a direction towards the row of the rolling elements 3.

[0234] Even in any one of the embodiments shown respectively in FIGS. 33and 34, the stack of the sealing devices 5 placed on the support table41 are spaced from each other a distance corresponding to the space Swhich in turn corresponds to the amount of protrusion of the annularprojection 16 e, and are not therefore magnetically attracted to eachother. Accordingly, as is the case with the embodiment shown in FIG. 31,the sealing devices 5 can be automatically press-fitted into theassociated bearings one at a time smoothly. It is to be noted that theannular projection 16 e of the type discussed above can be equallyemployed in the sealing device 5 of any one of the embodiments accordingto the second to fourth aspects of the present invention.

[0235] Also, instead of the use of the annular projection 16 e or thediscontinuous projections 16 g, the core metal 12 which is a metallicmember mounted on the side of the fixed member may be made of anon-magnetic material. Examples of this non-magnetic material are many,but austenite stainless steels are preferred because they have acorrosion resistance effective to suppress rusting. Of those austenitestainless steel materials, SUS 304 now on mass production is morepreferred because of a required strength. The structure in which thecore metal 12 is made of the non-magnetic material can be equallyapplied to the various embodiments according to the first to fourthaspects of the present invention shown in FIGS. 1, 15, 21 and 23,respectively.

[0236] Where the core metal 12 is made of the non-magnetic material, andwhen the sealing devices 5 are stacked on the support table 41, eventhough the magnetized portion, that is, the rubber magnet 14 or themagnetized portion 14A magnetized directly in the slinger 11 in one ofthe sealing devices 5 is brought into contact with the core metal 12made of the non-magnetic material in the other of the sealing devices 5that is positioned immediately above such one of the sealing devices 5,the magnetic force of attraction emanating from the magnetized portiondoes not act on the core metal 12 made of the non-magnetic material.Accordingly, the neighboring sealing devices 5 will not be magneticallyattracted and, therefore, the sealing devices 5 can be supplied into thechute one at a time by the handling device of the automaticpress-fitting machine with no trouble to thereby accomplish an automaticpress-fitting of the sealing device 5 into the bearing.

[0237] Although the present invention has been fully described inconnection with the preferred embodiments thereof with reference to theaccompanying drawings which are used only for the purpose ofillustration, those skilled in the art will readily conceive numerouschanges and modifications within the framework of obviousness upon thereading of the specification herein presented of the present invention.Accordingly, such changes and modifications are, unless they depart fromthe scope of the present invention as delivered from the claims annexedhereto, to be construed as included therein.

What is claimed is:
 1. A wheel bearing which comprises an inner member,an outer member, a circular row of rolling elements interposed betweenthe inner and outer members, and a sealing device for sealing an annularend space delimited between the inner and outer members, said sealingdevice comprising: first and second annular sealing plates securedrespectively to one of the first and second members and the otherthereof, and disposed in face-to-face relation to each other; each ofthe first and second annular sealing plates including a cylindrical walland a radial wall assembled together to represent a generally L-shapedsection; the first annular sealing plate being mounted on one of theinner and outer members which is rotatable relative to the other of theinner and outer members, with the radial wall positioned on one sideadjacent an exterior of the bearing; a first elastic member mixed with apowder of magnetic particles and bonded by vulcanization to the radialwall of the first annular sealing plate, the first elastic member beingformed with a magnetized portion in which opposite magnetic poles areformed alternately in a direction circumferentially thereof; the secondsealing plate including an elastic sealing member, the elastic sealingmember being formed integrally with a side sealing lip slidinglyengageable with the radial wall of the first annular sealing plate and aradial sealing lip slidingly engageable with the cylindrical wall of thefirst annular sealing plate; the cylindrical wall of the second annularsealing plate being spaced a slight radial gap from a free periphery ofthe radial wall of the first annular sealing plate; and a second elasticmaterial made of a material different from that of the first elasticmember bonded to the radial wall and interposed at an engagement of thefirst annular sealing plate with such one of the first and secondmembers which is rotatable.
 2. The wheel bearing as claimed in claim 1,wherein the second elastic member interposed at the engagement of thefirst annular sealing plate comprises a coated layer of rubber materialapplied to the first annular sealing plate.
 3. The wheel bearing asclaimed in claim 1, wherein the second elastic member interposed at theengagement of the first annular sealing plate comprises a layer of paintmaterial applied to the first annular sealing plate and having a rustpreventive property.
 4. The wheel bearing as claimed in claim 3, whereinthe paint material is a polyethylene rubber paint.
 5. The wheel bearingas claimed in claim 1, wherein the second elastic member interposed atthe engagement of the first annular sealing plate comprises a layer ofadhesive material applied to the first annular sealing plate and havinga rust preventive property.
 6. The wheel bearing as claimed in claim 5,wherein the adhesive material is a resinous room temperature settingadhesive having an anaerobic property.
 7. The wheel bearing as claimedin any one of claims 3 to 6, wherein a surface of the first annularsealing plate which forms the engagement has a surface roughness notgreater than Rmax 3.0.
 8. The wheel bearing as claimed in claim 1,wherein the inner member has an outer peripheral surface formed with anannular groove and wherein the second elastic member of the differentmaterial is a ring-shaped rubber member, the first annular sealing platebeing mounted on the inner member through the ring-shaped rubber member.9. The wheel bearing as claimed in claim 1, wherein an annular jointbetween the cylindrical wall and the radial wall of the first sealingplate is provided with a folded portion that extends radially inwardlyfrom the radial wall and joined to the cylindrical wall after havingbeen turned backwards; wherein an annular depression is formed on anouter peripheral end surface of the inner member by radially inwardlydepressing to provide a reduced diameter portion; wherein the firstannular sealing plate is mounted on the inner member with the foldedportion positioned within the annular depression; and wherein the secondelastic member of the different material is a ring-shaped rubber memberthat is interposed between an annular side face of the annulardepression and the folded portion.
 10. The wheel bearing as claimed inclaim 1, wherein an annular depression is formed on an outer peripheralend surface of the inner member by radially inwardly depressing toprovide a reduced diameter portion; wherein the first annular sealingplate is mounted on the annular depression with the cylindrical wallthereof engaged with an outer peripheral surface of the annulardepression; and wherein the second elastic member of the differentmaterial is a ring-shaped rubber member that is interposed between anaxial free end of the cylindrical wall of the first annular sealingplate and an annular side face of the annular depression.
 11. The wheelbearing as claimed in claim 1, wherein the cylindrical wall of the firstannular sealing plate is formed with a stop member which is in turnengaged in an annular groove defined on the outer peripheral surface ofthe inner member.
 12. The wheel bearing as claimed in claim 11, whereinthe stop member comprises a bent end formed at an axial free end of thecylindrical wall of the first annular sealing plate.
 13. The wheelbearing as claimed in claim 11, wherein the stop member comprises aplurality of protuberances formed on the cylindrical wall of the firstannular sealing plate at a position generally intermediate of an axiallength of the cylindrical wall and spaced a distance from each other ina direction circumferentially of the cylindrical wall of the firstannular sealing plate.
 14. The wheel bearing as claimed in claim 11,wherein the stop member comprises an annular projection formed in thecylindrical wall of the first annular sealing plate at a locationgenerally intermediate of an axial length of the cylindrical wall andextending circumferentially of the cylindrical wall.
 15. A wheel bearingwhich comprises an inner member, an outer member, a circular row ofrolling elements interposed between the inner and outer members, and asealing device for sealing an annular end space delimited between theinner and outer members, said sealing device comprising: first andsecond annular sealing plates secured respectively to one of the firstand second members and the other thereof, and disposed in face-to-facerelation to each other; each of the first and second annular sealingplates including a cylindrical wall and a radial wall assembled togetherto represent a generally L-shaped section; the first annular sealingplate being mounted on one of the inner and outer members which isrotatable relative to the other of the inner and outer members, with theradial wall positioned on one side adjacent an exterior of the bearing;a first elastic member mixed with a powder of magnetic particles andbonded by vulcanization to the radial wall of the first annular sealingplate, the first elastic member being formed with a magnetized portionin which opposite magnetic poles are formed alternately in a directioncircumferentially thereof; the second sealing plate including an elasticsealing member, the elastic sealing member being formed integrally witha side sealing lip slidingly engageable with the radial wall of thefirst annular sealing plate and a radial sealing lip slidinglyengageable with at least one of the cylindrical wall of the firstannular sealing plate and said one of the inner and outer members whichis rotatable; the cylindrical wall of the second annular sealing platebeing spaced a slight radial gap from a free periphery of the radialwall of the first annular sealing plate; and the elastic sealing memberhaving an elastic projection formed therewith so as to extend outwardlytherefrom, the elastic projection being elastically engaged with aconnecting member that is held in contact with an annular axial end faceof the inner member.
 16. The wheel bearing as claimed in claim 15,wherein the connecting member is a constant speed universal couplinghaving a shoulder that is held in contact with the annular axial endface of the inner member.
 17. The wheel bearing as claimed in claim 15,wherein the connecting member is a crimped portion of a barrel hub whichis crimpled radially outwardly to confront an axial end of a separateinner race then held in abutment with one end of the barrel hub.
 18. Thewheel bearing as claimed in claim 15, wherein the elastic projection iselastically held in contact with an outer peripheral surface of theconnecting member.
 19. The wheel bearing as claimed in claim 15, whereinthe elastic projection is elastically held in contact with a side faceof the connecting member.
 20. The wheel bearing as claimed in claim 15,wherein the radial sealing lip of the second sealing plate is slidinglyengaged with the inner member.
 21. A wheel bearing which comprises aninner member, an outer member, a circular row of rolling elementsinterposed between the inner and outer members, and a sealing device forsealing an annular end space delimited between the inner and outermembers, said sealing device comprising: first and second annularsealing plates secured respectively to one of the first and secondmembers and the other thereof, and disposed in face-to-face relation toeach other; each of the first and second annular sealing platesincluding a cylindrical wall and a radial wall assembled together torepresent a generally L-shaped section; the first annular sealing platebeing mounted on one of the inner and outer members which is rotatablerelative to the other of the inner and outer members, with the radialwall positioned on one side adjacent an exterior of the bearing; a firstelastic member mixed with a powder of magnetic particles and bonded byvulcanization to the radial wall of the first annular sealing plate, thefirst elastic member being formed with a magnetized portion in whichopposite magnetic poles are formed alternately in a directioncircumferentially thereof; the second sealing plate including an elasticsealing member, the elastic sealing member being formed integrally witha side sealing lip slidingly engageable with the radial wall of thefirst annular sealing plate and a radial sealing lip slidinglyengageable with the cylindrical wall of the first annular sealing plate;the cylindrical wall of the second annular sealing plate being spaced aslight radial gap from a free periphery of the radial wall of the firstannular sealing plate; and of the first and second annular sealingplates, at lest the first annular sealing plate being prepared from asteel plate made of a magnetic material, the steel plate having asurface formed with a metallic layer made of metal having a Yong'smodulus of elasticity that is lower than that for the one of the firstand second members which is rotatable.
 22. The wheel bearing as claimedin claim 21, wherein the metallic layer is a metal plated layer.
 23. Thewheel bearing as claimed in claim 21, wherein the metal having the lowerYoung's modulus of elasticity is selected from the group consisting ofzinc, tin, gold, silver and copper.
 24. The wheel bearing as claimed inclaim 21, wherein the metallic layer has a thickness within the range of5 to 30 μm.
 25. The wheel bearing as claimed in claim 21, wherein asurface of the first annular sealing plate which forms the engagementhas a surface roughness not greater than Rmax 3.0.
 26. The wheel bearingas claimed in claim 21, wherein a surface of the engagement of one ofthe first and second members, which is rotatable, with the first annularsealing plate is formed as a ground surface which has been plunge cut.27. The wheel bearing as claimed in claim 26, wherein a surface of theone of the first and second members, which is rotatable, that is engagedwith the annular sealing plate has a surface roughness not greater thanRmax 3.0.
 28. A wheel bearing which comprises an inner member, an outermember, a circular row of rolling elements interposed between the innerand outer members, and a sealing device for sealing an annular end spacedelimited between the inner and outer members, said sealing devicecomprising: first and second annular sealing plates secured respectivelyto one of the first and second members and the other thereof, anddisposed in face-to-face relation to each other; each of the first andsecond annular sealing plates including a cylindrical wall and a radialwall assembled together to represent a generally L-shaped section; thefirst annular sealing plate being mounted on one of the inner and outermembers which is rotatable relative to the other of the inner and outermembers, with the radial wall positioned on one side adjacent anexterior of the bearing; a first elastic member mixed with a powder ofmagnetic particles and bonded by vulcanization to the radial wall of thefirst annular sealing plate, the first elastic member being formed witha magnetized portion in which opposite magnetic poles are formedalternately in a direction circumferentially thereof; the cylindricalwall of the second annular sealing plate being spaced a slight radialgap from a free periphery of the radial wall of the first annularsealing plate; and the second sealing plate including an elastic sealingmember, the elastic sealing member being formed integrally with a sidesealing lip slidingly engageable with the radial wall of the firstannular sealing plate and a radial sealing lip slidingly engageable withan outer peripheral surface of the one of the inner and outer members,which is rotatable, and adjacent an engagement surface of the firstannular sealing plate with such one member.
 29. The wheel bearing asclaimed in claim 28, wherein an annular depression of a depthcorresponding to a thickness of the first annular sealing plate isformed on the one of the first and second members, which is rotatable,and wherein the cylindrical wall of the first annular sealing plate ispress-fitted around an outer peripheral surface of the annulardepression.
 30. The wheel bearing as claimed in claim 28, wherein theradial sealing lip of the second sealing plate is inclined so as toextend outwardly of the bearing.
 31. The wheel bearing as claimed inclaim 28, wherein the side sealing lip of the second annular sealingplate is provided at two locations spaced radially.
 32. The wheelbearing as claimed in claim 28, wherein the first annular sealing plateis made of a ferrite stainless steel.
 33. The wheel bearing as claimedin claim 28, wherein at least one of a free peripheral edge of theradial wall of the first annular sealing plate and the cylindrical wallof the second sealing plate is provided with an overhang portion definedby a portion of the elastic member integrated with the annular sealingplate and wherein a maximum diameter portion of the free peripheral edgeof the radial wall of the first annular sealing plate including thisoverhang portion has a diameter greater than a minimum diameter portionof an axial free end of the cylindrical wall of the second annularsealing plate and is positioned inwardly of the bearing form the minimumdiameter portion.
 34. A sealing device included in a wheel bearing asdefined in claim 1, wherein one of the first and second annular sealingplates which is on a fixed side is made of a metal and wherein saidfixed side annular sealing plate or the elastic sealing member mountedthereon is formed with a projection protruding inwardly of the wheelbearing, said projection being formed so as to be continuous ordiscontinuous.
 35. A sealing device included in a wheel bearing asdefined in claim 15, wherein one of the first and second annular sealingplates which is on a fixed side is made of a metal and wherein saidfixed side annular sealing plate or the elastic sealing member mountedthereon is formed with a projection protruding inwardly of the wheelbearing, said projection being formed so as to be continuous ordiscontinuous.
 36. A sealing device included in a wheel bearing asdefined in claim 21, wherein one of the first and second annular sealingplates which is on a fixed side is made of a metal and wherein saidfixed side annular sealing plate or the elastic sealing member mountedthereon is formed with a projection protruding inwardly of the wheelbearing, said projection being formed so as to be continuous ordiscontinuous.
 37. A sealing device included in a wheel bearing asdefined in claim 28, wherein one of the first and second annular sealingplates which is on a fixed side is made of a metal and wherein saidfixed side annular sealing plate or the elastic sealing member mountedthereon is formed with a projection protruding inwardly of the wheelbearing, said projection being formed so as to be continuous ordiscontinuous.
 38. A sealing device included in a wheel bearing asdefined in claim 1, wherein one of the first and second annular sealingplates which is on a fixed side is made of a metallic non-magneticmaterial.
 39. A sealing device included in a wheel bearing as defined inclaim 15, wherein one of the first and second annular sealing plateswhich is on a fixed side is made of a metallic non-magnetic material.40. A sealing device included in a wheel bearing as defined in claim 21,wherein one of the first and second annular sealing plates which is on afixed side is made of a metallic non-magnetic material.
 41. A sealingdevice included in a wheel bearing as defined in claim 28, wherein oneof the first and second annular sealing plates which is on a fixed sideis made of a metallic non-magnetic material.
 42. A sealing device asclaimed in claim 34, wherein in place of the first elastic memberincluding the magnetized portion, the magnetized portion is formed bydirectly magnetizing the radial wall of the one of the first and secondannular sealing plates which is on a rotatable side.
 43. A sealingdevice as claimed in claim 35, wherein in place of the first elasticmember including the magnetized portion, the magnetized portion isformed by directly magnetizing the radial wall of the one of the firstand second annular sealing plates which is on a rotatable side.
 44. Asealing device as claimed in claim 36, wherein in place of the firstelastic member including the magnetized portion, the magnetized portionis formed by directly magnetizing the radial wall of the one of thefirst and second annular sealing plates which is on a rotatable side.45. A sealing device as claimed in claim 37, wherein in place of thefirst elastic member including the magnetized portion, the magnetizedportion is formed by directly magnetizing the radial wall of the one ofthe first and second annular sealing plates which is on a rotatableside.